Polymer dispersed liquid crystal (PDLC) display element for use in an electronic apparatus

ABSTRACT

A polymer dispersed liquid crystal (PDLC) display element for use in an electronic apparatus wherein the display element operates in a PDLC mode or reverse PDLC mode providing for reduction of visual display haze, improved display contrast. The particular medium includes a liquid crystal portion and a polymer portion and may include a chiral component. In cases where visual display haze and contract is a particular problem in the utility of the reverse PDLC display element, such as in the case where the display element is combined with a solar battery, a sufficient amount of dichroic dye is added to the liquid crystal portion of the medium, and, further, a compound showing no fluorescence emission with respect to a liquid crystal portion, or a polymer or a chiral polymer precursor portion of the medium, is employed. The resulting electronic apparatus can, therefore, incorporate a reverse PDLC type display element in combination with a solar battery or other component that affects display quality in such elements to improve the overall visual quality and contrast in the display rendering the display more useful in more miniaturized applications.

This is a continuation of application Ser. No. 08/346,598 filed Nov. 29,1994, now U.S. Pat. No. 5,686,017, which is a continuation ofInternational Application No. PCT/JP94/00505, filed Mar. 29, 1994.

BACKGROUND OF THE INVENTION

1. Related Application

This application is a continuation of International Application No.PCT/JP94/00505, filed Mar. 29, 1994.

2. Technical Field

This invention relates to reflective type, bright display elementsuseful as a display in wrist watches, meter display panels of vehicles,information display terminals for electronic memorandum books orcomputer notebooks, computers and televisions, or information bulletinboards, and to the construction and configuration of electronicapparatus employing such display elements as provided in a visualdisplay, such as a LCD panel.

BACKGROUND

Various kinds and styles of wrist watches or time pieces, such asanalog-type of watches with hand pointers and digital-type of watchesequipped with liquid crystal display elements, have been developed andoffered as time-keeping products. Recently, in addition to thesestandard types of watches, hybrid-type of watches have also beendeveloped which are equipped with a smaller LC (liquid crystal) windowfor display because of other types of information to be displayed. Also,there has been developed the two-layer type watches with a liquidcrystal display element superposed on the surface of analog-type watchhaving hand pointers for indicating time. As examples, see JapaneseLaid-Open Patent Application Nos. 94940/1979, 136718/1979, 26986/1980,46845/1980, 188786/1980, 23024/1981 and 65618/1981. In the field ofwatches and electronic memorandum books, there have recently beendeveloped various kinds of multi-functional type of watches capable ofcarrying out different kinds of informational functions. For thesemulti-functional uses in connection with watches, it is expected thatthe development of novel type of display elements may become the newpractice and trend in future watch design.

On the other hand, displays employed in electronic apparatus forspecialized display use, such as a meter panel for an automobile, areneeded to display various kinds of information within a limited space.Furthermore, particularly in automotive meter panels, the display modeto be employed should be selected to be either analog type or digitaltype.

In addition, in the field of information devices including watches, thecurrent trend has been toward a more compact and portable type ofstructure with concurrent demand for reducing electric energyconsumption of the display element to be mounted in these devices. Insuch portable information display devices or information processingapparatus, batteries have been conventionally employed. Therefore, thelifetime of batteries to be used is an important factor in their use.From this viewpoint of energy saving, devices incorporating a solarbattery have recently been developed. In an apparatus disclosed inJapanese Patent Publication No. 61930/1991, for example, a liquidcrystal display element and a solar battery are incorporated together inorder to provide saving of space in the apparatus. In Japanese Laid-OpenPatent Application No. 106725/1988, for example, there is disclosed anapparatus having a structure wherein a solar battery is designed tosurround a LC display element.

Practical embodiments of such an apparatus employ liquid crystalmaterial dispersed in polymer, which is then encapsulated in the liquidcrystal display element. These encapsulated mediums are referred to asPolymer Dispersed Liquid Crystal ("PDLC") mediums. These types ofmediums provide for a bright, reflective-type display element requiringno polarizing plates suitable for the use in these types of liquidcrystal display elements. PDLC display elements are of two modes. Onemode is the type of medium that becomes transparent to transmissivelight in the presence of an applied electric field and scatters light inthe absence of an applied electric field, as illustrated in JapanesePatent Publication No. 501631/1983. Another mode, which is referred toas "reverse PDLC", is the type that scatters light in the presence of anapplied electric field and absorbs light or becomes transparent to lightin the absence of a field, as illustrated in Japanese Laid-Open PatentApplication No. 227684/1992 relating to a gel network type of reversePDLC, Japanese Laid-Open Patent Application No. 119302/1993 relating toparticle-orientation/dispersion type of reverse PDLC, and U.S. Pat. No.4,994,204 relating to a liquid crystal droplet-dispersion type ofreverse PDLC. For the purpose of increasing birefringence of liquidcrystals and polymers of these PDLC modes as well as improving theirdegree of light scattering, liquid crystals or polymers having aterphenyl skeleton or a terphenyl skeleton containing a hetero atom areemployed.

Conventional hybrid-type watches may be provided with separate analogdisplay and digital display portions and, therefore, individual displayareas are reduced in size to accommodate spacing rendering it moredifficult to see the displayed information. In addition, since thedigital display portion is of the twisted nematic type employing apolarizing plate, the displayed image appears darker, further decreasingits visibility. Furthermore, the incorporation of a solar battery insuch a hybrid-type watch, while desirable, is more difficult due tolimitations on available space. A solar battery has been previouslyincorporated with a liquid crystal display element in such hybrid-typewatches in the past. However, the liquid crystal display elementincorporated with such a solar battery provides for low transmittancelevels. For example, a twisted nematic type liquid crystal using apolarizing plate had a transmittance of 30% or less and a guest-hosttype liquid crystal had a transmittance of 60% or less, resulting in acomparatively lower production efficiency of electric power of the solarbattery. Also, since the display mode employs a dark reflector as abackground, such as the solar battery itself, the visibility of thewatch display becomes even more reduced. In addition, in case where aliquid crystal display element utilizing dynamic scattering effect issuperposed on a solar battery, the display principle accompanies ionicflow, and, therefore, requires an increase in electric power consumptionof the battery. From these reasons, the integration of a liquid crystaldisplay element with a solar battery has not been, in practice,successful.

In the case where the display portion of electronic apparatus has aspecial utility, such as an on-vehicle-type meter display panel, both ananalog and digital display are sometimes incorporated into a single,limited display space. In this situation, it is necessary to provide alarger display space.

Recently, car navigation systems, on-vehicle television receivers andvideo projectors have come into use. In general, the displays of theseelectronic apparatus are placed near the central region of the vehicleconsole section. As a result, the vehicle driver must turn his head toalign his/her eyes toward the passenger's seat in order to observe thedisplay, which may be dangerous since the eyes are not momentarilyobserving the roadway.

Also, conventional on-vehicle-type meter display panels and the likeemploy a self-emissive light system or a backlight system to render thedisplayed information more visible. This results in the disadvantagethat the display of the panel can not be seen well in the daytime,particularly when the outside ambient light is very bright. In addition,users may desire to select either an analog or digital type of displayaccording to their individual taste or desires.

Conventional PDLC or reverse PDLC compounds used in PDLC displayelements have a fluorescence emission in the visible region, such ascompounds having a terphenyl skeleton, for purposes of improvingbirefringence or for mismatching of the refractive indices between theemployed liquid crystal material and the polymer. As a result,noticeable fluorescence and haze in the transparent state is produced.Therefore, a good transparent state in the display system can not becreated so that the display contrast is reduced. For example, in a PDLCdisplay element or panel, the transparency in the presence of an appliedvoltage becomes low. When a light absorbing layer is placed at the backsurface of the element, the color of the background appears turbid dueto the fluorescence and haze caused by this particular kind of liquidcrystal layer.

Moreover, in the case of a reverse PDLC display element or panel,because of the fluorescence and haze of this kind of liquid crystallayer, the degradation of the transparent state in the absence of anapplied voltage results so that when a light absorbing layer is placedat the back surface of the element, the color of the background alsoappears turbid due to the fluorescence and haze created by the liquidcrystal layer. Also, a reverse PDLC display element containing adichroic dye mixed with the liquid crystal and including a lightreflective layer positioned at the back surface provides the problemthat the color state with the dichroic dye appears turbid in the absenceof applied electric field due to fluorescence and haze created by theliquid crystal layer, resulting in degradation of the display contrast.

In the employment of conventional techniques for the purpose ofimproving scattering degree in the scattering mode of the display, a lowmolecular weight, chiral component is placed in the liquid crystalmedium. During the preparation process, a polymer precursor incorporatedwith the liquid crystal compound is polymerized to increase theproportional content of the low molecular weight, chiral component inthe liquid crystal. The increase in the proportional content of the lowmolecular weight, chiral component reduces the chiral pitch in theliquid crystal. As the result, a mismatch between the twist structure ofthe polymer at the initial stage of polymerization as compared to afterthe polymerization is produced, resulting in creation of haze in thedisplay element in a transparent state in the absence of an appliedelectric field. Furthermore, such a change in the chiral pitch caused bya low molecular weight, chiral component is temperature dependent, whichcauses changes, particularly increases, in the amount of display haze.

The creation of haze, therefore, is a serious problem in atransparent-scattering, switching mode PDLC medium containing nodichroic dye. For example, in the case used as a cover glass and aclockface of a watch, a haze generated in a transparent state of adisplay element makes the production value remarkably deteriorate. Incase of a display element containing dichroic dye with a reflectivelayer on its back surface, the display element employs the modes ofswitching between light absorption and light scattering. However, evenin this case, the creation of the fluorescence and haze effect alsoremarkably deteriorates contrast in the light absorbing state of thedisplay.

Accordingly, it is an object of this invention to provide a novel PDLCor reverse PDLC display element having brighter display quality,particularly in its light scattering state, compared to previously knownPDLC and reverse PDLC display elements, as well as providing lessfluorescence and haze effect in its transparent state while improvingoverall display contrast. Moreover, the liquid crystal/polymer medium isprovided to have high reliability, enhancing the reliability of thedisplay element so that different active elements or a color filter maybe effectively employed to provide a display element having multipleutility in various different types of electronic apparatus.

Another object of this invention is the provision of an electronicapparatus having lower power consumption with improved display qualityand life by combining a reverse PDLC display element which is highlylight transmissive so as to be employed with any one of a plurality ofdifferent types of electronic apparatus having its own display apparatusand/or with an underlying solar battery.

A further object of this invention is provision of a technique forimproving the visibility of a display in an electronic apparatus,particularly in bright ambient light.

SUMMARY OF THE INVENTION

According to this invention, a display element for employment with anelectronic apparatus is fabricated by mixing together a polymer orpolymer precursor and a liquid crystal material, placing the resultingmixed solution in its liquid crystalline state between a pair of spacedelectrodes to produce a PDLC or a reverse PDLC display element, andbring about a phase separation of the polymer from the liquid crystal,wherein dichroic dye is added to the liquid crystal to provide fortransmitted light absorption is in the range of about 1% to 20% in theabsence of an applied electric field. The display element of thisinvention is further includes the use of a chiral component thatprovides for a chiral pitch in the liquid crystal before phaseseparation that is approximately identical to a chiral pitch in theliquid crystal after phase separation. Moreover, a low molecular weight,chiral component and chiral polymer precursor are employed as the chiralcomponents to provide for chiral pitch. These chiral components aremixed with the polymer precursor and liquid crystal material, and thepolymer precursor is polymerized in the liquid phase by means forpolymerization so that the chiral polymer precursor is incorporated intothe resulting polymerized polymer portion and the low molecular weight,chiral component is incorporated into the liquid crystal portion.

The chiral component employed in this invention is less temperaturesensitive in the temperature range of operation of the display so thatambient temperature changes cause only a 20% or less change in thechiral pitch. Further, at least two kinds of chiral components havingopposite temperature dependency effects on the chiral pitch relative toeach other are employed as the chiral component in the liquidcrystal/polymer medium in order to reduce the amount of chiral pitch.

In the display element of this invention, compounds exhibiting afluorescence quantum yield of 0.3 or less are employed as the liquidcrystal and polymer materials in the total amount of not less than 60%by weight. Examples of compounds exhibiting 0.3 or higher of afluorescence quantum yield contain a terphenyl, anthracene or peryleneskeleton or the like. If such compounds are employed as liquid crystaland polymer materials, very large emissions of fluorescence would becreated resulting in a significant deterioration in display contrast. Onthe other hand, in the present invention, compounds exhibiting a 0.3 orless of fluorescence quantum yield are employed having a biphenyl ortolane skeleton, being the principal liquid crystal and polymermaterials, or those having a terphenyl skeleton are contained in anamount of 10% or less in the liquid crystal and polymer materials.

Relative to other attributes of the present invention, the displayelement PDLC material may be a polymer that is particulate in form, ormay take on the form of coupled or chain connected particles, orparticle aggregates, or a gel-network form. The liquid crystal may bedispersed throughout the polymer in droplet form. As previouslyindicated, the display element the PDLC medium includes a chiralcomponent in the liquid crystal. Also, the liquid crystal may alsoinclude a dichroic dye. Furthermore, the display element may alsoinclude a light absorbing plate, such as a solar battery, at its rear orback surface. The display element may include a group of electrodesformed on a surface of a pair of substrates which are supported inspatial relation with the liquid crystal/polymer medium therebetween,wherein one of the substrates is made of reflective material.

The electronic apparatus including the display element of this inventionmay utilize a liquid crystal medium, e.g., a PDLC medium or a reversePDLC medium, that is transparent in the absence of applied electricfield with a solar battery placed in superposed relation with thedisplay element to form part of the information display image, or thedisplay element may be the surface cover itself for any type of otherdisplay apparatus. The display element is fabricated by placing a mixedliquid solution of a polymer or polymer precursor and liquid crystalmaterial between a pair of spaced electrodes, and then causing a phaseseparation of the polymer from the liquid crystal utilizing means tobring about phase separation. Furthermore, the electronic apparatus ismay be provided with a layer, preferably made of a transparent or highlyrefractive material, is placed on the back surface of the displayelement or between a back surface (e.g., a solar battery) and the PDLCdisplay element.

The display element and the electronic apparatus utilizing the displayelement of this invention may have the display viewing surface on theobserver or front side of the display element subjected to a non-glaretreatment and/or an anti-reflection treatment. Also, at least one of thesubstrates employed in the display element may have a color filterformed on its surface in facing relation with the liquid crystal/polymermedium. Further, at least one of the substrates employed in the displayelement is provided with active elements formed on its surface incontact with the liquid crystal/polymer medium.

Furthermore, the display element and the electronic apparatus utilizingthe display element of this invention may utilize a liquid crystalcontaining one or more of the following compounds: ##STR1## wherein n isan integer; R represents an alkyl, alkoxy, cycloalkyl or cycloalkoxygroup; R₁ and R₂ independently represent an alkyl, cycloalkyl, alkoxy orcycloalkoxy group or H or F; and X represents H, F, Cl or CN.

The display element and the electronic apparatus are also characterizedin that the polymer is prepared for polymerization employing at leastone polymer precursor selected from the following compounds: ##STR2##wherein R and R' independently represent H or CH₃ ; B, B' and B"independently represent OCO, COO, OCONH, NHCOO, CONH, NHCO, --C.tbd.C--,an alkyl group, O, N or S; and A₁ and A₂ independently represent a groupcontaining aromatic ring, such as phenyl, biphenyl, terphenyl,quaterphenyl, naphthalene or anthracene, which may be partiallysubstituted by a halogen, alkyl or cyano group.

Other objects and attainments together with a fuller understanding ofthe invention will become apparent and appreciated by referring to thefollowing description and claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a display element structure for a panel according toExample 2 of this invention, employing a TFT's as the active element.

FIG. 2 illustrates a display element structure for a panel according toExample 5 of this invention.

FIG. 3 is a graphic illustration and comparison of the electro-opticcharacteristic of the display elements according to Example 5 andComparative Example 5.

FIG. 4 is a graphic illustration and comparison of the electro-opticcharacteristic of the display elements according to Example 6 andExample 7.

FIG. 5 is a graphic illustration and comparison of the electro-opticcharacteristic of the display elements according to Example 8 andComparative Example 6.

FIG. 6 illustrates a display element structure for a panel according toExample 12 of this invention, employing a MIM element.

FIG. 7 illustrates a display element structure for a panel according toExample 22, utilizing a color filter and a MIM element.

FIG. 8 is a sectional view of a display element structure for theinformation processing apparatus according to Example 23.

FIG. 9 is a schematic illustration of a display element structure forthe information display apparatus according to Example 24.

FIG. 10 is a schematic illustration of a display element structure forthe information display apparatus according to Example 25.

FIG. 11 is a sectional view of a display element structure for theinformation display apparatus according to Example 26.

FIGS. 12, 13 and 14 each schematically illustrate differentconfigurations of a display element of this invention for the electronicapparatus according to Example 27.

FIGS. 15, 16 and 17 each schematically illustrate differentconfigurations of a vehicle meter display panel according to Example 28.

FIG. 18 is a graphic illustration showing the incidence angle dependencyof reflectance for incident light on a flat substrate surface of adisplay element.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is now illustrated in more detail by reference to thedrawings with respect to the following description.

According to the present invention, in a reverse PDLC display medium,the turbidity of the display in the absence of an applied electric fieldcan be significantly reduced by adding a sufficient amount of dichroicdye to the medium or by employing a liquid crystal or polymer in themedium having a low fluorescence quantum yield. The amount of addeddichroic dye varies depending on the intended use and application. Inthe case where a display element must be transparent in the absence ofan applied electric field with an attended reduction on haze, as forexample, in the case where a solar battery or other type of displayapparatus is positioned on the back surface of the display element, itis preferred that the dichroic dye mixed into the liquid crystal providefor a light absorption in the resulting display element in the range ofabout 1 to 20%, preferably in the range of about 5 to 10%, whereby thehaze becomes less conspicuous without impairing the transparency of thedisplay. On the other hand, in the case where a reflective layer ispositioned on the back surface of the display element to absorb thelight in the absence of an applied electric field, dichroic dye is mixedwith the liquid crystal so that the light absorption quality of theresulting display element becomes not less than 20% providing for goodcontrast.

On the other hand, the turbidity of a display element in the absence ofan applied electrical field can also be reduced by the employment ofliquid crystal or polymer material exhibiting a small fluorescencequantum yield. Specific examples of such compounds include liquidcrystals and polymer precursors having skeleton which provide afluorescence quantum yield of approximately 0.3 or less, such as atolane skeleton or biphenyl skeleton. If the compounds employedexhibiting a fluorescence quantum yield over 0.3, e.g. liquid crystalsand polymer precursors having a terphenyl skeleton, are employed,fluorescence emission is observed in the display state in the absence ofan applied field, resulting in undesirable display contrast.

In the process of producing a reverse PDLC medium having a low molecularweight, chiral component, the polymer precursor in the liquid crystal isthereafter polymerized to become a polymer so that a proportional amountof the low molecular weight, chiral component contained in the liquidcrystal becomes higher and the chiral polymer precursor in the liquidcrystal is incorporated into the polymer so that a proportional amountin the liquid crystal is reduced. Therefore, the content ratio of thechiral component in the liquid crystal remains constant even with theoccurrence of polymerization and also the chiral pitch remains constant.As a result, the twisted structure of polymer in the initial stage ofthe polymerization is identical to that in the liquid crystal after thepolymerization, and the creation of haze in the transparent state in theabsence of an applied field becomes remarkably small.

In the case where the employed chiral component is temperature dependentexhibiting a small change in chiral pitch depending on temperaturechange, the orientation state of the liquid crystal becomes difficult tochange, depending upon the amount of temperature change, after thereverse PDLC medium has already been produced. Therefore, the employmentof a chiral component according to this invention renders it possible toprevent the creation of displayed haze caused by operating orenvironmental temperature changes. It is preferred to employ a chiralcomponent exhibiting a chiral pitch change of 20% or less in theoperating or environmental temperature range of the display element.

A reverse PDLC medium is almost transparent in the absence of an appliedelectric field. Accordingly, in the case where a reverse PDLC medium inthe form of display element 21 is placed on the surface of a displayapparatus, as in the case of FIG. 10 showing analog mode watch 26 withhour/minute hands, an observer can easily view displayed information indisplay element 26 beneath the reverse PDLC element 21. When an electricfield is applied to the reverse PDLC medium, an observer canconcurrently see both the information display beneath the reverse PDLCmedium of element 21 and the white display of the reverse PDLC element21 in the foreground. The foreground display of element 21 is producedby light scattering in the reverse PDLC medium.

In this case, when a reflective layer, especially a transparent layer 29having a high refractive index, is placed between the back surface ofthe display apparatus, comprising a back surface analog watch mode 26with hour/minute hands, and the front surface reverse PDLC displayelement 21, as illustrated in FIG. 12, incident light on the displayapparatus effectively enters into reverse PDLC display element 21 and,as the result, the display appears bright with good contrast. Since theincident light on the front of the display is not reflected too much,analog display 26 positioned at the back surface can be easily seen andvisually read. This phenomenon can be understood better with referenceto FIG. 18, showing the incidence angle-dependency of reflectance forlight incident to a flat substrate surface. As can be seen from FIG. 18,as the angle of incidence increases, so does the amount of reflectionfrom transparent layer 29. However, at incident angles that aresubstantially normal to the surface being viewed or even at more acuteangles of incident, the transparency of layer 29 is substantially goodfor providing good visibility of clockface 26 via PDLC display element21 and layer 29. The results in FIG. 18 were determined by calculationaccording to Fresnel's formula on the assumption that the refractiveindex of the substrate is 2 and is in contact with air (refractiveindex=1) wherein natural light was decomposed into two orthogonalpolarized light components for purposes of the calculation. Since layer26 is transparent, the back surface display 26 beneath reverse PDLCdisplay element 21 is never difficult to view. Of course, an equivalentdisplay property with good visible display quality can be realized bymeans of multiple display elements 21 and 26 superposed on each other inany sequential arrangement, which sequential arrangements areillustrated by the respective arrangements shown in FIGS. 12, 13 and 14.

In the case where the liquid crystal in the reverse PDLC medium alsocontains dichroic dye, the liquid crystal layer is changed to a lightabsorbing state through the control of an applied electric field so thatthe display of information caused by light scattering is provided in amanner illustrated in FIG. 9. In FIG. 9, the reverse PDLC displayelement 21 is between the front surface analog watch mode 26 withhour/minute hands and the back surface solar battery 22. Of course, thedisplay can be rendered even more clear by the incorporation of a highlyrefractive layer 29 into the structure as shown in FIG. 8. In place of areverse PDLC medium, a conventional PDLC medium may be used. In thiscase, however, in order to make clear a display at the back surface thedisplay apparatus, the liquid crystal layer containing dichroic dye ischanged into a transparent state by the control of an applied electricfield in a manner opposite to that described for a reverse PDLC medium.

The reverse PDLC medium of the present invention is transparent in theabsence of an applied electric field. Accordingly, when a displayelement having a reverse PDLC medium is placed on the surface of a solarbattery, the production efficiency of electric power of the solarbattery will less impaired. As previously describe, the solar batteryand the display element can be superposed on one other. As the result,not only is a savings in space and miniaturization of the electronicapparatus employing the display element realized, but also the utilityof design and application of the electronic apparatus can be more freelyachieved.

In the structures of the display elements and the electronic apparatusdescribed above, active elements or a color filters may be formed oneither substrate employed with the reverse PDLC medium to increase thedisplay capacity of the display element and to provide a color display.When such a display element is applied to a display for a vehiclenavigation system, a motorist can view a road map displayed on thesystem display without turning his/her head or attention away from thefront view of the road so that safe driving conditions can be maintainedby the motorist. Of course, these display elements have application totelevision as well as application with solar batteries to an electronicmemorandum book or a laptop computer without running down the batterysupply.

In addition, in the structures of the display elements and theelectronic apparatus previously described, an anti-reflection treatmentor a non-glare treatment may be applied to the surface substrate toimprove visibility of the display elements.

EXAMPLE 1

This embodiment is a display element in which dichroic dye is mixed in atrace amount in order to make the haze of a reverse PDLC inconspicuous.In particular, in this embodiment, a liquid crystal composition to beused in Examples 2 to 4 is explained in the followings. That is, aguest-host type liquid crystal was prepared by mixing 99.25 wt % of aTL202 (trade name) BL007 (trade name) mixture (7:3), both being producedby Merck Limited, as a liquid crystal, 0.25 wt % of G470 (a product ofNippon Kanko Shikiso Kenkyusho), 0.4 wt % of SI512 (a product of MitsuiToatsu Senryo) and 0.1 wt % of M137 (a product of Mitsui Toatsu Senryo)as dichroic dyes. To 98 wt % of the resulting liquid crystal, was added2 wt % of CNL617 (a product of Asahi Denka Kogyo, K.K.) as a chiralcomponent and then mixed with each other, to give a chiral guest-hostliquid crystal.

In case of a display element is combined with active element, theskeleton of a liquid crystal to be employed should be those having highreliability. As such liquid crystal, chlorine-based biphenyl liquidcrystals such as TL202, TL205, TL213, TL215 and TL216 (products of MerckLimited) are preferably used. In addition, there may be used RDP 80616and RDP 10248 (products of Rodic Inc.) and SS 5004 (a product of ChissoCorporation) as liquid crystal having high reliability, and BL007 (aproduct of Merck Limited) as highly birefractive liquid crystal. Inother uses, liquid crystals having any skeleton may be used so long asthey satisfy the driving voltage and birefractive index. Specificexamples of liquid crystal compounds to be employed are those containingthe following compounds ("F_(n) " indicating that fluorines may belocated at any point on any of the benzene nucleus): ##STR3##

In the above-listed formulae, R represents an alkyl, cycloalkyl, alkoxyor cycloalkoxy group; R₁ is an alkyl or alkoxy group, or hydrogen orfluorine; X represents a cyano group, halogen, hydrogen or a nitrogroup; and n is an integer. In addition, liquid crystals having negativedielectric anisotropy may be used as the liquid crystal. In thisprocess, the alignment treatment to be subjected to the substratesurface is preferably the homeotropic alignment treatment.

As a dichroic dye to be used, any one may be used so long as it exhibitsdichroism. However, from viewpoint of light resistance, as shown in thisExample, anthraquinone based, naphthoquinone based, and perylene baseddichroic dyes are preferred. Furthermore, for the purpose of depressinga haze, dichroic dyes of dark tone and having a low fluorescence quantumyield are more preferable. In the case where a solar battery is used asthe background, in order to prevent the lowering of productionefficiency of electric power, the amount of dichroic dye to be mixedwith liquid crystal is preferably the minimum amount to depress a haze.The degree of haze depends on the kinds of liquid crystals, polymerprecursors, chiral components and polymerization conditions to beemployed. Therefore, the concentration of the dichroic dye should beadjusted according to the actual circumstances.

As the chiral component to be used, any one may be used so long as itcan twist the orientation of the liquid crystal, in an adequate amount.Preferably, the chiral component is those which can twist theorientation of a liquid crystal layer preferably by 90°, and morepreferably 270°, in the direction of liquid crystal thickness. Examplesof such chiral component include, for example, S811, R811, S1011, R1011,CB15, C15 and CE2 (products of Merck Limited), CM series (a product ofChisso Corporation), and CNL series (a product of Asahi Denka Kogyo,K.K.).

As the polymer precursor to be mixed with the above-described liquidcrystals, any one may be used so long as it can be polymerized in theliquid crystal by irradiation of light, electron beam and heat andcontains in its molecule a large mesogenic moiety having birefringency.The moiety to be polymerized of the polymer precursor is acrylate,methacrylate, crotonate, cinnamate, epoxy or the like; and the mesogenicmoiety is phenyl, biphenyl, terphenyl, quaterphenyl, or the like. In theA present invention, a suitable substituted group may be introduced intothe polymer precursor for the purpose of improving birefringency andsolubility with the liquid crystal. In particular, a polymer precursorin which the moiety to be polymerized and the mesogenic moiety arebonded directly, the resulting polymer tends to become particulate. Onthe other hand, a polymer precursor in which the moiety to bepolymerized and the mesogenic moiety are connected through a spacer,such as an alkyl chain or a polymer precursor having plural of moietiesto be polymerized in one molecule, the resulting polymer tends to form agel-network structure. Examples of the former polymer precursors includethe following compounds: ##STR4## wherein R and R' independentlyrepresent H or CH₃ ; B, B' and B" independently represent OCO, COO,OCONH, NHCOO, CONH, NHCO, --C.tbd.C--, an alkyl group, O, N or S; and A₁and A₂ independently represent a group containing aromatic ring, such asphenyl, biphenyl, terphenyl, quaterphenyl, naphthalene or anthracene,which may be partially substituted by halogen, alkyl or cyano group.

As the latter polymer precursors, among the monomers listed above, thosewhich are di-functional and those which contain a spacer such as alkylgroup between the moiety to be polymerized and the mesogenic moiety maybe employed. Examples of commercially available polymer precursorsinclude, for example, Aronix™ and Resedamacromonomer™ produced byToagosei Chemical Industry Co., Ltd.; KAYARAD™ and KAYAMER™ produced byNippon Kayaku Company, Ltd.; NOPCOMER™, SICOMET™ and PHOTOMER™ producedby San Nopco Limited; Eptohto, Neotohto and Daptohto produced by TohtoKasei Co., Ltd.; ADEKA™ RESIN, ADEKA™ OPTOMER and ADEKA™ OPTON producedby Asahi Denka Kogyo, K.K.; 2200 series produced by Threebond Limited;Ripoxy™ and Spirac™ produced by Showa Highpolymer Co., Ltd.; productproduced by Nippon Polyurethane Inc., Co., Ltd. These monomers may bemixed in part with the former monomers, i.e., monomers in which theresulting polymers become particulate in nature. In addition, otherpolymers, such as thermoplastic polymers, e.g. ethyl cellulose, may alsobe employed.

Comparative Example 1

A liquid crystal composition is prepared according to Example 1, exceptemploying no dichroic dye. Other materials and fabrication conditionswere same as Example 1.

EXAMPLE 2

In this embodiment, a polymer particle dispersed type of reverse PDLCmedium was made employing the liquid crystal composition of Example 1,and then its haze condition was examined. In particular, a liquidcrystal mixture was prepared by using biphenyl methacrylate as thepolymer precursor indicated in Example 1 in an amount of 7 wt %, andthen placed into a gap provided in a panel as shown in FIG. 1 and thensealed. At first, the fabrication process for the panel is explainedwith reference to FIG. 1. A transparent electrode is formed on thesurface of substrate 1. Next, the surface of electrode 2 was subjectedto an alignment treatment. Subsequently, on another substrate 8, TFTelements were formed as an active element comprising gate electrode 15,gate insulation layer 18, semi-conductive layer 16, source electrode 14,drain electrode 17. Aluminum was vapor-deposited to form reflectiveelectrodes 7. The surface of electrodes 7 were subjected to an alignmenttreatment. Substrates 1 and 8 were spatially supported relative to eachother along their peripheries with their electrode surfaces in facingrelationship forming a 5 μm gap between their facing surfaces. In thisembodiment, the thickness of liquid crystal/polymer precursor mixedlayer 3, inserted into the gap or spacing, was, therefore, set to 5 μm.However, the thickness may be suitably set within the range from 3 μm to10 μm depending on the intended application. Liquid crystal/polymerprecursor mixed layer 3 was irradiated with UV radiation having awavelength in the range of 300 nm-400 nm and 3.5 mW/cm² in its liquidcrystal phase, bring about phase separation of polymer particles fromthe liquid crystal. On the back surface rear surface of the displayelement, a solar battery was placed as a light-absorbing plate and thesurface of the battery was subjected to a non-glare treatment and ananti-reflection treatment. Of course, these treatments are not alwaysrequired or necessary, and either of these treatments can significantlyimprove the visibility of the display element.

A 5 V driving voltage was applied to the liquid crystal/polymer layer,and then light was directed from a inclined direction of 20° based onthe normal line of the display element surface, to determined thereflection light intensity to the normal line direction. As the result,the brightness was 30% based on that of a white paper. On the otherhand, when the driving voltage was adjusted to 0 V to give a blackdisplay state, the reflectance measured was 4%.

In this embodiment, the alignment treatment employed a polyimidealigning film and was carried out in the manner that a polyimidealigning film was formed and then was subjected to a rubbing treatment.However, in the general alignment treatment, other kinds of aligningfilms may be employed, or only an applied rubbing treatment on thesurfaces in contact with the reverse PDLC medium may be used withoutemploying any aligning film, or a LB film or an oblique evaporation filmmay be employed.

The light absorbing reflective plate to be placed on the back surface ofthe display element is not necessarily be a solar battery. A lightabsorbing plate applied with a light reflection treatment on its surfaceis also preferably used. The plate other than the light-absorbingreflective plates may also be used. For example, reflective plates madeof aluminum, chromium and the like may be used. In case of reflectiveplates having high reflectance, visibility of the resultant can beimproved by increasing in the amount of dichroic dye to be added.

In the display element of the present invention, color display becomespossible by forming a color filter on the substrate. In this case, asthe colors to be used for the color filter, any one may be employed solong it shows good visibility according to the intended use, as well asthe color combination which can reproduce full colors. The color filterto be used is preferably composed of materials exhibiting no absorptionin the UV region.

In the present invention, the display element is applied with anon-glare treatment and a anti-reflection treatment on its surface.However, such treatments are not so essential, and the display elementwithout such treatments will exhibit good display properties.

In apparatus having small-to-medium size capacity, such as in the caseof a watch, sufficient information can be given even if an activeelement is not formed thereon.

The active element to be used is not limited to the TFT element hereshown, and other TFT elements having other structures, transistors, MIMelements, ferroelectric elements and the like may also be used. As asubstrate material to be formed with such active elements on itssurface, materials such as glass, silicon, arsenic gallium andgermanium, other inorganic substances and organic substances, such asplastics, may be employed. In the display element according to thisinvention, all the circuit drivers and controller circuitry can beformed directly on the substrates. Therefore, by using the displayelement, a display apparatus can be fabricated at low cost.

Comparative Example 2

A reverse PDLC was fabricated according to Example 2 using the liquidcrystal composition of Comparative Example 1. The resulting reverse PDLCmedium was examined its electro-optic characteristics in the same manneras Example 2. As the result, the brightness was 35% based on that of awhite paper in the presence of an applied electric field. Thereflectance in the absence of an applied electrical field was 8%.

EXAMPLE 3

A polymer gel network aligned type of liquid crystal display element wasfabricated using the liquid crystal composition of Example 1.

That is, a display element was fabricated in the same manner as Example2, using the liquid crystal composition of Example 1, 5 wt % of M6200 (aproduct of Toagosei Chemical Industry Co., Ltd.) as a polymer precursorand 2 wt % of 184 Irugacure (a product of Ciba Geigy Co.) as aphoto-polymerization initiator.

To the liquid crystal/polymer layer of the resulting display element, a10 V of driving voltage was applied, and then light was entered from thedirection inclined by 20° based on the normal line of the displayelement surface, to determined the reflection light intensity to thenormal line direction. As the result, the brightness was 28% based onthat of a white paper in the presence of an applied electric field. Thereflectance under a black display state in the absence of an appliedelectrical field was 8% the brightness was 28% based on that of a whitepaper.

In this embodiment, the polymer precursor to be used may be othercompound which can make a gel network effectively, as shown inExample 1. Other conditions were same as those of Example 2.

Comparative Example 3

A display element was fabricated according to Example 3, except usingthe liquid crystal composition of Comparative Example 1. The resultingdisplay element showed a reflectance under the white display state of33%, and a reflectance under the black display state of 5%.

EXAMPLE 4

A display element, in which droplets of the liquid crystal were alignedand dispersed in the polymer, was fabricated using the liquid crystalcomposition, and examined its haze.

In particular, in the liquid crystal/polymer precursor mixture ofExample 1, a mixture comprising 30 wt % of M6200 (a product of ToagoseChemical Industry Co., Ltd.) as a polymer precursor and 2 wt % ofIrugacure 184™ (a product of Ciba Geigy Co., Ltd) as aphoto-polymerization initiator were employed. In this embodiment, otherconditions were same as Example 2 to fabricate a display element.

To the liquid crystal/polymer layer of the resulting display element, a20 V of driving voltage was applied, and then light was entered from thedirection inclined by 20° based on the normal line of the displayelement surface, to determined the reflection light intensity to thenormal line direction. As the result, the brightness was 28% based onthat of a white paper. The reflectance under a black display state inthe absence of an applied electrical field was 10%.

In this embodiment, the polymer precursor to be used may be othercompound which can make a gel network effectively, as shown inExample 1. Other conditions were same as those of Example 2.

Comparative Example 4

A display element was fabricated according to Example 4, except usingthe liquid crystal composition of Comparative Example 1. The resultingdisplay element showed a reflectance under the white display state of33%, and a reflectance under the black display state of 15%.

EXAMPLE 5

In this embodiment, are fabricated a reverse PDLC in which atolane-based liquid crystal and a tolane-based polymer was used. FIG. 2simply illustrates a partial sectional view of the display elementaccording to this embodiment.

At first, a panel in which a liquid crystal/polymer precursor is to beinserted is explained in the followings. A transparent electrode havinga desired pattern was formed on a substrate, and then a rubbingtreatment was applied to the surface of the resultant. Two substratesthus fabricated were fixed at their peripheries with setting theirelectrode sides face-to-face and keeping a 4 μm gap therebetween.

Next, the liquid crystal and polymer precursor to be inserted into thepanel are explained in the followings. As for the liquid crystal, wasused a tolane-based liquid crystal comprising the following compoundgroup I: ##STR5## wherein R and R' independently represent an alkylgroup having 1 to 12 carbon atoms;

the following compound group II: ##STR6## wherein R and R' independentlyrepresent an alkyl group having 1 to 12 carbon atoms; and

the following compound group III: ##STR7## wherein R represents an alkylgroup having 1 to 12 carbon atoms; Ar represents phenyl, pyridine andpyrimidine; and X represents F or H,

as a mixture in a mixing ratio of 47 wt %: 33 wt %: 20 wt %,respectively. Each compound group to be used in this embodiment wascomposed of some compounds, and the number of carbon atoms of individualalkyl groups and their mixing ratio are shown in the followings:

Compound group I:

(R=1, R'=11) 2%

(R=3, R'=2) 8%

(R=4, R'=1) 8%

(R=4, R'=2) 9%

(R=4, R'=3) 5%

(R=5, R'=1) 8%

(R=5, R'=3) 5%

(R=5, R'=11)2%;

Compound group II:

(R=3, R'=2) 21%

(R=4, R'=2) 12%; and

Compound group III:

(R=4) 6%

(R=5) 7%

(R=7) 7%.

In this embodiment, the alkyl groups employed were straight chain type.However, branched type of alkyl groups may also be employed. With 98.5wt % of the resulting liquid crystal, 1.5 wt % of a chiral component,R1011 (a product of Merck Limited), was mixed. With 95 wt % of thischiral liquid crystal, the following compounds, as polymer precursors,were mixed in the mixing ratio of 3.3 wt % and 1.7 wt %, respectively,to give a liquid crystal/polymer precursor mixture: ##STR8##

Subsequently, the mixture thus prepared was inserted into theaforementioned panel and sealed under a reduced pressure. Thereafter, UVradiation of 300 nm to 400 nm in wave length and 3.5 mW/cm² in intensitywas irradiated to the resulting panel for 10 minutes to polymerize thepolymer precursors.

On the back surface of the display element thus fabricated, a blacklight-absorbing plate was placed. Light was entered from the directioninclined by 20° based on the normal line of the display element surfaceto detect the light reflected to the normal direction, whereby a graphshowing the electro-optic characteristic shown in FIG. 3 was given. Inthe graph of FIG. 3, the solid line indicates the electro-opticcharacteristic of the display element according to this embodiment. Asshown in FIG. 3, since the transmittance was extremely high at thethreshold voltage or below, the black caused by the light absorbingplate placed on the back surface of the display element and, as theresult, the contrast was 27.

The liquid crystal and polymer precursor to be used may be thoseindicated in Example 1. Among these, those which exhibit a lowfluorescence quantum yield in the visible region and a highbirefringence are preferable. In particular, those which have tolane orbiphenyl skeleton in its molecule are more preferable. On the contrary,undesirable compounds are those which exhibit a high fluorescencequantum yield in the visible region, for example, compounds havinganthracene, terphenyl or quaterphenyl skeleton or the compounds in whichphenyl groups are connected to one another. On the other hand, in thecompound groups I to III shown above, the combination of R and R' ofalkyl groups or the mixing ratio of compounds is not limited to thoseindicated above, and may vary according to experimental and operationalconditions such as temperature range of liquid crystal phase, drivingvoltage. In addition, other compounds may be mixed therewith.

As for chiral component, the kind and the mixing ratio are not limitedto those indicated this embodiment, and those indicated in Example 1 mayalso be employed: they can vary according to the intended use.

The thickness of the liquid crystal/polymer layer is not limited to 4μm, and may vary within the range of 2 μm to 20 μm, according to theintended use. With the decrease in thickness of the liquidcrystal/polymer layer, the transparency in the absence of an appliedvoltage is increased, whereas the scattering degree is reduced. Oh theother hand, with the increase in the thickness, the scattering degree isincreased, whereas the driving voltage required and the cloudiness inthe absence of an applied electric field are increased.

The alignment treatment to be applied to the electrode surface may becarried out in such a manner that an aligning film is provided and arubbing treatment is applied on the film.

The black absorption plate to be placed on the back surface of thedisplay element may be a solar battery or other reflective material.

Comparative Example 5

This is a comparative embodiment to Example 5. In this embodiment, aliquid crystal containing terphenyl skeleton compound was employedcomprising a mixture of TL202 (a product of Merck Limited) and4-cyano-4"-pentyl-terphenyl (T15) in amounts of 80 wt % and 20 wt %,respectively. With 95 wt % of this liquid crystal composition, weremixed 4-terphenylmethacrylate and terphenyl-4,4"-dimethacrylate aspolymer precursors in amounts of 3.3 wt % and 1.7 wt %, respectively.Other conditions are same as those in Example 5.

The display element, thus fabricated, was examined for its electro-opticcharacteristic in the same manner as Example 5. The results are shown inFIG. 3 by the broken line. The display element was transparent at thethreshold voltage or below, but fluorescence was observed in the visibleregion. As the result, the black background appeared whitish and thecontrast was reduced by a value of approximately 3.

EXAMPLE 6

The display element fabricated in this embodiment is one in which atolane-based liquid crystal showing no fluorescence emission in thevisible region and a terphenyl-based polymer precursor showingfluorescence emission in the visible region are employed. As the liquidcrystal, one indicated in Example 5 was used. As the polymer precursor,terphenyl methacrylate and terphenyl dimethacrylate were used. Otherconstituent conditions were same as those of Example 5.

The display element thus fabricated was examined its electro-opticcharacteristic, and the results were shown in FIG. 4 as a solid line.When compared with the results of Example 5, the black display at thethreshold voltage or below was somewhat whitish and the contrast waslower, having a contrast value of approximately 12.

EXAMPLE 7

The display element fabricated in this embodiment is one in which atolane-based polymer showing no fluorescence emission in the visibleregion and a terphenyl-based liquid crystal showing fluorescenceemission in the visible region are used. As the liquid crystal, oneindicated in Comparative Example 5 was used. As the polymer precursor,tolane-based one indicated in Example 5 was used. Other constituentconditions were same as those of Example 5.

The display element thus fabricated was examined its electro-opticcharacteristic, and the results were shown in FIG. 4 as a broken line.The contrast was approximately 6.

EXAMPLE 8

The display element fabricated in this embodiment is one in which aliquid crystal and a polymer precursor showing less fluorescenceemission in the visible region are used. As the liquid crystal, was usedone indicated in Example 5. A polymer precursor was employed having thefollowing formula: ##STR9##

Other conditions were same as those of Example 5. The display element,thus fabricated, was examined for its electro-optic characteristic whichis shown by the solid line in FIG. 5.

In this embodiment, any polymer precursor can be used so long as it canform a gel network structure when polymerized. In particular, thepolymer precursors capable of making a gel network structure moreeffectively are those in which two polymerized moieties are containedand the moieties are combined through a long alkyl spacer. Thedi-functional monomers indicated in Example 1 are especially preferable.Also, the embodiment of this example can be utilized in otherembodiments of this invention.

Comparative Example 6

The display element fabricated in this embodiment is fabricated in thesame manner as Example 6, except a liquid crystal exhibiting a largefluorescence emission in the visible region was utilized. The liquidcrystal employed was E7 (a product of Merck Limited) which containspentyl terphenyl carbonitrile which exhibits fluorescence emission.

The fabricated display element was examined for its electro-opticcharacteristic, and the results are shown in FIG. 5 as a broken line.When compared with the display element of this Comparative Example, thedisplay element of Example 8 is found to be of improved contrast.

EXAMPLE 9

The display element of this embodiment is fabricated according toExample 5, in which dichroic dye was mixed with the liquid crystal andthe electrodes formed on the substrates were formed with reflectivematerial, i.e., a display element which absorbs light, i.e., the lightabsorbing mode, in the absence of an applied electric field. The panelwas fabricated according to the procedures of Example 2.

After rendering the gap of the panel under a reduced pressure, theliquid crystal/polymer precursor mixture indicated in Example 5 wasfurther mixed with dichroic dyes of M361:SI512:M137 (products of MitsuiToatsu Senryo) having the mixing ratio 1.5:1.7:0.43 (wt %), and theresulting mixture was inserted into the panel and sealed. The UVradiation of 300 nm to 400 nm in wave length and 3.5 mW/cm² in intensitywas irradiated to this panel at 40° C. for 10 min., whereby the polymerprecursor was polymerized and the resulting polymer separated out fromthe liquid crystal.

A non-glare film which had been subjected to anti-reflection treatmentwas applied on the surface of the resulting display element and then alight-absorbing layer was placed on the back surface of the displayelement thereby completing the display panel. When a circuit driver andcontroller were powered for driving of display element and a computerare connected to the display panel, the computer screen could be viewed.Of course, if this display apparatus is connected to a television tuner,the television screen can be viewed.

The dichroic dye employed in this embodiment is preferably ananthraquinone-based or perylene-based dye exhibiting a good lightresistance, and more preferably one that exhibits good dichroism andsolubility. The mixing amount of the dichroic dye into the liquidcrystal should be considered to ensure optimized contrast.

In this embodiment, a reflective layer to be placed on the back surfaceof the liquid crystal/polymer layer doubled as an electrode. However, italso be possible to use a transparent electrode and place a reflectivelayer on the back surface of the display element.

In addition, a substrate on which an active element is formed can beplaced either side of the liquid crystal/polymer layer.

A non-glare treatment and an anti-reflection treatment may be applied ifnecessary.

EXAMPLE 10

The display element of this embodiment employs the liquid crystal andthe polymer precursor of Example 8, and further contains dichroic dyeand uses the panel of Example 9. The liquid crystal and polymer employedwere same as those of Example 8. With 96.7 wt % of the liquid crystal,dichroic dyes M361, SI512 and M34 (products of Mitsui Toatsu Senryo)were mixed in amounts of 1.3:1.6:0.4 (wt %), respectively. Into thepanel fabricated in Example 9, the resulting liquid crystal/polymerprecursor mixture was inserted and sealed. The UV radiation wasirradiated to this panel, to give a display element. A non-glare filmwhich had been subjected to an anti-reflection treatment was applied onthe surface of the resulting display element and then a light-absorbinglayer was placed on the back surface of the display element: thus adisplay apparatus, to which the display element of the present inventionwas applied, was accomplished. When a driver, a controller, an electricpower for driving of display element and a computer (any of these beingnot shown in the drawings) are connected to this display apparatus, thecomputer screen could be displayed. Of course, if this display apparatusis connected to a television tuner, the television screen can be seen.

EXAMPLE 11

This embodiment is a display element incorporated with the hazereduction technique of the present invention. At first, a liquid crystalis explained. As a liquid crystal, a mixture of RDP80616-2 (a product ofRodic Inc.) and ML1009 (a product of Merck Limited), which both areliquid crystal showing a low fluorescence emission in the visibleregion, in a mixing ratio of 7:3 was used. With this liquid crystalmixture, 0.25 wt % of G470 (a product of Nippon Kanko Shikiso Kenkyujo),0.4 wt % of SI512 (a product of Mitsui Toatsu Senryo) and 0.1 wt % ofM137 (a product of Mitsui Toatsu Senryo) were mixed as dichroic dyes, togive a guest-host type liquid crystal. With the resulting liquidcrystal, 2 wt % of CNL611 (a product of Asahi Denka Kogyo, K.K.) showinga low temperature dependency in chiral pitch was further mixed, wherebya chiral guest-host type liquid crystal was prepared. With this liquidcrystal, butylphenyltolane methacrylate and biphenyl dimethacrylate aspolymer precursors and the following compound as a chiral polymerprecursor were mixed in amounts of 3.3 wt %, 1.7 wt % and 0.3 wt %,respectively. ##STR10##

The resultant was inserted into the panel and sealed. The UV radiationwas irradiated to this panel at 50° C. The display element thusfabricated may be subjected to a non-glare treatment or ananti-reflection treatment on its surface.

On back surface of the resulting display element, a solar battery wasplaced, to give a reflection type of display element. This displayelement was determined for reflectance in the absence of an appliedelectric field in the same manner as Example 2. As the result, thereflectance at 20° C. was 1%. This display element could be used forsegment display for watch by application of an electric field.Furthermore, this display element could employ a solar battery placed onits back surface as a driving power source for liquid crystal.

In this embodiment, an active element was not used. However, if used,same effect might be given. In such case, the liquid crystal having agood retention characteristic should be used, as shown in Example 1. Ifincorporating with a color filter, a bright color display can beprovided. In the case where no active element is used, any material maybe employed as a liquid crystal so long as it shows a nematic typeliquid crystal phase.

The thickness of the liquid crystal/polymer layer is preferably 3 to 10μm. Too thin layer leads a low scattering property, whereas too thicklayer not only makes the required driving voltage higher but also makedecrease in contrast; which are practically disadvantageous.

In stead of the solar battery, a light absorbing layer and/or a lightreflective layer may be placed on the back surface of the displayelement. If without placing anything on the back surface, this displayelement can also display as white scattering on a transparent glass.

In this embodiment, other materials and fabrication conditions were sameas those of Example 12. The chiral components shown in Example 15 mayalso be used in this embodiment.

EXAMPLE 12

The display apparatus of this embodiment is one combining a displayelement in which polymer is dispersed as particles orparticles-connected aggregations into a liquid crystal containingdichroic dye with an active element, to which a chiral polymer precursoris further applied. FIG. 6 is a simple sectional view of a panel for thedisplay apparatus of the present invention n which a MIM element isformed. At first, a panel was fabricated. A transparent electrode 2 wasformed on a substrate 1, and then subjected to a alignment treatment. Asthe alignment treatment, a conventional method utilized for a TN-typeliquid crystal display element. In this embodiment, a polyimide film wasformed on the electrode and the treated surface was subjected to arubbing process. Subsequently, on the opposite substrate 8, 480×640pieces of MIM element as active element and a reflection electrode 7were formed, by which the alignment treatment was applied. A layer forprotecting the active element may be applied on the resultant.Thereafter, these substrates were fixed at their peripheries to eachother as remaining the sealing inlet with keeping a 5 μm gaptherebetween. Next, the liquid crystal/polymer precursor mixture isexplained. As the liquid crystal, a mixture of TL213 and MJ91261(products from Merck Limited) in a mixing ratio of 8:2. With 97 wt % ofthis mixture, 3 wt % of S811 (a product from Merck Limited) as a chiralcomponent was mixed to give a chiral liquid crystal. With 96.3 wt % ofthe resulting liquid crystal, M361, SI512 and M34 (products of MistToatsu Senryo) as dichroic dyes were further mixed in amounts of 1.5 wt%, 1.7 wt % and 0.5 wt %, respectively. To 93 wt % of thus resultingguest-host type chiral liquid crystal, were dissolved biphenylmethacrylate as a polymer precursor and the following compound as achiral polymer precursor in amounts of 6.86 wt % and 0.14 wt %,respectively: ##STR11##

The resultant was inserted into the panel fabricated above. This panelwas irradiated with UV radiation (300 nm to 400 nm of wave length; 3.5mW/cm² in intensity) from the substrate 1 side at 50° C. to polymerizethe polymer precursor in the liquid crystal; thus a display element wasfabricated. This display element was subjected to an anti-reflectiontreatment on its surface. This treatment is not always necessary.

The reflectance of this display element determined in the absence of anapplied electric field was 3% at 20° C. When a driver for driving ofliquid crystal and a controller circuit were connected to the displayelement, the computer screen could be displayed brightly and with goodcontrast. Of course, the display element can also be used for terminalsfor a television or a game machine. If a color filter is incorporated todisplay element, a bright color display can be given.

As the chiral component, liquid crystal and polymer precursor to be usedin this embodiment, those described in Examples 1 and 15 can be used.

As for the content of the dichroic dye, in the case where the displayelement is used mainly for the transmission in the absence of an appliedelectric field, for example, in the case whereas solar battery is usedas a reflective plate or other display apparatus is further placed, thecontent of the dichroic dye is cut down to improve the electric powerproduction efficiency of the solar battery or to improve the visibilityof the display apparatus. For other uses, as described in thisembodiment, light absorption in the absence of an applied electric fieldis fully done so that the effective contrast can be provided.

Other chiral polymer precursors may be employed such as the followingcompounds: ##STR12##

The derivatives of these compounds can also be used, for example, thosein which phenyl or biphenyl in the compounds listed above is changedinto phenyl, biphenyl or terphenyl skeleton, and those in which thestructure of alkyl groups in these compounds are modified. The amount ofthe chiral polymer precursor to be mixed is determined so that thechiral pitch of the liquid crystal part becomes identical to that of thepolymer precursor part. For example, a low molecular weight chiralcomponent S811, a product of Merck Co., shows a chiral pitch ofapproximately 10 μm when it is mixed with a liquid crystal in an amountof 1 wt % based on the amount of the liquid crystal. On the other hand,the chiral polymer precursor used in this embodiment shows a chiralpitch of approximately 20 μm when it is mixed with a liquid crystal inan amount of 1 wt % based on the amount of the liquid crystal.Accordingly, in order to adjust the both chiral pitches identical, 3 wt% of the low molecular weight chiral component S811, a product of MerckCo., is mixed a liquid crystal to adjust its chiral pitch toapproximately 3 μm, and 6 wt % of the chiral polymer precursor is mixedwith a polymer precursor to adjust the chiral pitch of the polymerprecursor to 3 μm. That is, in the stage before polymerization, thepolymer precursor is dissolved in a liquid crystal, and the amount ofthe liquid crystal is the sum of the amount of the low molecular weightliquid crystal and that of the polymer precursor. Therefore, the amountof chiral component to cause to twist them is the sum of the amounts ofthe low molecular weight chiral component and the chiral polymerprecursor. In the polymerization step by a polymerization means, thepolymer precursor and the chiral polymer precursor are polymerized tophase-separate out from the liquid crystal layer and removed. As theresult, the chiral component remained in the liquid crystal is only thelow molecular weight chiral component. Accordingly, the chiral pitch inthe liquid crystal does not change.

On the contrary, in the conventional techniques, compared with thistechnique, since no chiral polymer precursor is used, a polymerprecursor dissolved in a liquid crystal, and the amount of the liquidcrystal is the sum of the amounts of a low molecular weight liquidcrystal and the polymer precursor. Accordingly, the amount of chiralcomponent to cause to twist them is only that of the low molecularweight chiral component. In the polymerization step by a polymerizationmeans, the polymer precursor is polymerized to phase-separate out fromthe liquid crystal layer and to be removed. In spite of reducing theamount of the liquid crystal by the amount of the polymerizationprecursor, the amount of the low molecular weight component remainingtherein is not change. As the result, the chiral pitch in the liquidcrystal become short and the mismatch between the polymer and the liquidcrystal comes to occur.

The thickness of the liquid crystal/polymer layer is preferably 3 to 10μm. Too thin layer leads a low scattering property, whereas too thicklayer not only makes the required driving voltage higher but also leadsa decrease in contrast; which are practically disadvantageous.

The active element to be used in this embodiment is not limited to theMIM element indicated in this embodiment, and those which have atransistor structure, such as polysilicon TFT elements and amorphoussilicon TFT elements, those which have a MIM structure, ferroelectricelements may be used. The number of the active elements to be used isnot also limited to the number indicated in this embodiment, and it maydetermined according to the intended use. Of course, if without activeelement, the display element of this embodiment can display as a watchand an electronic memorandum book, as shown in below.

In this embodiment, the reflective electrode 7 may be a transparentelectrode, and a reflective layer may be placed on the back surface ofthe display element. The reflective layer may include also a lightscattering property. Of course, the reflective layer may be a solarbattery itself.

Comparative Example 7

The display element of this embodiment employs only S811, a product ofMerck Co. as a chiral component in Example 12. Concretely, with theguest-host type chiral liquid crystal of Example 1, 7 wt % of biphenylmethacrylate was mixed as a polymer precursor, to fabricate a displayelement in the same manner as Example 12.

The reflectance of the thus fabricated display element determined in theabsence of an applied electric field was 5% at 20° C.

EXAMPLE 13

The display element of the present invention is one in which a polymeris dispersed as particles or particles-connecting aggregations in aliquid crystal with no dichroic dye, to which a chiral polymer precursoris further used. A panel was fabricated according to Example 5. Themixture of a liquid crystal and a polymer precursor to be inserted intothe panel and sealed is explained as follows. A chiral liquid crystalwas prepared by mixing 98 wt % of RDP80616-2 (a product of Rodic Inc.)as a liquid crystal and 2 wt % of CNL611 (a product of Asahi DenkaKogyo, K.K.) as a chiral component to each other. With resulting chiralliquid crystal, were mixed buthylphenyltolane methacrylate and biphenyldimethacrylate as polymer precursors and the compound of Example 11 as achiral polymer precursor in amounts of 3.3 wt %, 1.7 wt % and 0.3 wt %,respectively. This mixture was inserted into the panel and sealed. Then,UV radiation was irradiated to the resulting panel at 50° C. The displayelement thus fabricated may be subjected to a non-glare treatment or ananti-reflection treatment on its surface.

On the back surface of this display element, was placed a solar battery.The resulting reflection-type display element was determined for itsreflectance in the absence of an applied electric field in the samemanner as Example 2. As the result, the reflectance at 20° C. was 1.8%.This display element could be used for segment display of a watch byapplying an electric field. Furthermore, in this display element, thesolar battery placed on its back surface could be used as a liquidcrystal-driving power source.

In this embodiment, no active element was used. However, if used, sameeffect might be given. In such case, the liquid crystal having a goodretention characteristic should be used, as shown in Example 1. Ifincorporating with a color filter, a bright color display can beprovided. In the case where no active element is used, any material maybe employed as a liquid crystal so long as it shows a nematic typeliquid crystal phase.

The thickness of the liquid crystal/polymer layer is preferably 3 μm to10 μm. Too thin layer leads a low scattering property, whereas too thicklayer not only makes the required driving voltage higher but also makedecrease in contrast; which are practically disadvantageous.

In stead of the solar battery, a light absorbing layer and/or a lightreflective layer may be placed on the back surface of the displayelement. This display element can also display without placing anythingon its back surface, as white scattering on a transparent glass.

In this embodiment, other materials and fabrication conditions were sameas those of Example 12. The chiral components shown in Example 15 mayalso be used in this embodiment.

Comparative Example 8

The display element of this embodiment is fabricated according toExample 13, except employing only a low molecular weight chiralcomponent as chiral component. That is, with the chiral liquid crystalof Example 13, butylphenyltolane methacrylate and biphenyldimethacrylate were mixed as polymer precursors in amounts of 3.4 wt %and 1.6 wt %, respectively. Other materials and fabrication conditionsemployed were the same as those of Example 13.

The display element thus fabricated was determined for its reflectancein the absence of an applied electric field. As the result, thereflectance was 3% at 20° C.

EXAMPLE 14

This embodiment is a display apparatus combining a display element inwhich a liquid crystal containing dichroic dye is dispersed in a polymergel network polymer with active element, to which a chiral polymerprecursor is incorporated. A panel with TFT element was fabricatedaccording to Example 9. The liquid crystal/polymer precursor mixture tobe inserted into the panel and sealed is explained as follows. A mixtureof TL205 and BL007 (products of Merck Limited) in a mixing ratio of 7:3was used as a liquid crystal. A chiral liquid crystal was prepared bymixing 98 wt % of the liquid crystal mixture with 2 wt % of CNL611 (aproduct of Asahi Denka Kogyo, K.K.) as a chiral component to each other.With 96.3 wt % of the resulting chiral liquid crystal, were mixed M361,M370 and M483 (products of Mitsui Toatsu Senryo) as dichroic dyes inamounts of 1.2 wt %, 2 wt % and 0.5 wt %, respectively, to give aguest-host type chiral liquid crystal. With 97 wt % of this guest-hosttype chiral liquid crystal, were mixed 3 wt % of a polymer precursor ofExample 8 and 0.1 wt % of the following compound as a chiral polymerprecursor. ##STR13##

The resulting mixture was inserted into the panel and sealed. The UVradiation (300 nm to 400 nm, 3.5 mW/cm²) was irradiated to this panelfrom the substrate 1 side at 50° C., to polymerize the polymer precursorin the liquid crystal: thus a display apparatus of this embodiment wasaccomplished. This display apparatus was subjected to a non-glaretreatment and an anti-reflection treatment on its surface. Thesetreatments is not always necessary.

This display apparatus was determined for its reflectance in the absenceof an applied electric field in the same manner as Example 1. As theresult, the reflectance was 3% at 20° C. When a driver for liquidcrystal driving and a controller circuit were connected to the displayapparatus, the computer screen could be displayed brightly and with goodcontrast. Of course, the display apparatus can also be used forterminals for a television or a game machine. If a color filter isincorporated to display element, a bright color display can be given.

As the chiral component, liquid crystal, polymer precursor, activeelement and other fabrication conditions to be employed in thisembodiment, those described in Example 12 can be employed. Inparticular, the chiral component may be those indicated in Example 15.

As for the content of the dichroic dye, in the case where the displayelement is used for mainly giving a the transmission in the absence ofan applied electric field, for example, in the case where a solarbattery is used as a reflective plate or other display apparatus isfurther placed, the content of the dichroic dye is cut down to improvethe electric power production efficiency of the solar battery or toimprove the visibility of the display apparatus. For other uses, asdescribed in this embodiment, light absorption in the absence of anapplied electric field is fully done so that the effective contrast canbe provided.

The thickness of the liquid crystal/polymer layer is preferably 3 μm to10 μm. Too thin layer leads a low scattering property, whereas too thicklayer not only makes the required driving voltage higher but also leadsa decrease in contrast; which are practically disadvantageous.

Comparative Example 9

This embodiment is a display element fabricated according to the processof Example 14, except using only a low molecular weight chiral componentas the chiral component. That is, With the guest-host type chiral liquidcrystal indicated in Example 14, 3 wt % of a polymer precursor employedin Example 8. Other materials and fabrication conditions employed weresame as those of Example 14.

The display element thus fabricated was determined for its reflectancein the absence of an applied electric field. As the result, thereflectance was 4% at 20° C.

EXAMPLE 15

This embodiment is a display element in which a liquid crystalcontaining no dichroic dye is dispersed in a polymer gel network polymerwith active element, to which a chiral polymer precursor isincorporated. At first, a panel into which a liquid crystal/polymerprecursor mixture was to be inserted and sealed was fabricated accordingto Example 5. The liquid crystal/polymer precursor mixture to beinserted into the panel and sealed is explained as follows. BL007 (aproduct of Merck Japan Limited) as a, liquid crystal was mixed with 10wt % of CM22 (a product of Chisso Corporation) and 2.5 wt % of CB15 (aproduct of Merck Japan Limited) as chiral components, to give a chiralliquid crystal. With this chiral liquid crystal, were mixed 3 wt % of apolymer precursor employed in Example 8 and 0.1 wt % of the followingcompound as a chiral polymer precursor. ##STR14## The resulting mixturewas inserted into the panel and sealed. The UV radiation was irradiatedon the resulting panel at temperature of 50° C. bring aboutpolymerization. This display apparatus may be subjected to a non-glaretreatment or an anti-reflection treatment on its surface.

The resulting display apparatus was determined for its reflectance inthe absence of an applied electric field in the same manner asExample 1. As the result, the reflectance was 1.5% at 20° C.

The chiral components used in this embodiment have the followingcharacteristics: both of CM22 and CB15 have an ability to cause theaxial rotation of a liquid crystal to the right; and CB15 tends to showa longer chiral pitch with increasing temperature, i.e. exhibiting apositive temperature dependency, whereas CM22 tends to show a shorterchiral pitch with increasing temperature, i.e. showing a negativetemperature dependency. Accordingly, like this embodiment, it ispreferable to add two or more kinds of chiral components having oppositetemperature dependency in chiral pitch relative to each other. Examplesof other chiral components having a negative temperature dependency inchiral pitch include CM22 (a product of Chisso Corporation) and thefollowing compounds: ##STR15##

FL519, CNL621, CNL617, CNL616, CNL623, CNL637, CNL638 and CNL639(products of Asahi Denka Kogyo, K.K). Examples of other chiralcomponents having a positive temperature dependency in chiral pitchinclude CM19 and CM20 (products of Chisso Corporation), CB15, C15, S811,S1001, R1011, S1082 and R1082 (products of Merck Limited). Other thanthese chiral components may also be used. In this embodiment, two kindsof chiral components were used. However, three or more kinds of chiralcomponents may be used in a mixture. Of course, the chiral componentshaving a very small temperature dependency in chiral pitch may also beused, as shown in Example 1.

The liquid crystal, polymer precursor, a panel and other materials andfabrication conditions to be employed in this embodiment were accordingto Example 13. The composition of chiral components indicated in thisembodiment can applied to the display elements in which polymerdisperses as particles or particles-connecting aggregations.

Comparative Example 10

This embodiment is a display element fabricated according to the processof Example 15, except using only a low molecular weight chiral componentas the chiral component. With the chiral liquid crystal indicated inExample 14, 3 wt % of a polymer precursor employed in Example 8. Othermaterials and fabrication conditions employed were same as those ofExample 15.

The display element thus fabricated was determined for its reflectancein the absence of an applied electric field. As the result, thereflectance was 3% at 20° C.

EXAMPLE 16

This embodiment is a display element in which a liquid crystalcontaining dichroic dye is dispersed in a polymer matrix, wherein achiral polymer precursor and active element are incorporated. A panelinto which a liquid crystal/polymer mixture was to be inserted wasfabricated in the same manner as Example 12. The liquid crystal/polymerprecursor mixture to be inserted into the panel is explained as follows.A mixture of TL213 and MJ91261 (products of Merck Limited) in a mixingratio of 8:2 was used as a liquid crystal. A chiral liquid crystal wasprepared by mixing 98 wt % of the liquid crystal mixture with 2 wt % ofCNL617 (a product of Asahi Denka Kogyo, K.K.) as a chiral component witheach other. With 96.4 wt % of the resulting chiral liquid crystal, weremixed M361, S1512 and M34 (products of Mitsui Toatsu Senryo) as dichroicdyes in amounts of 1.5 wt %, 1.7 wt % and 0.4 wt %, respectively, togive a guest-host type chiral liquid crystal. With 77.6 wt % of thisguest-host type chiral liquid crystal, were mixed 20 wt % of M6200 (aproduct of Toagosei Chemical Industry Co., Ltd.) as a polymer precursor,0.4 wt % of the following compound as a chiral polymer precursor and 2wt % of Irugacure 184 (a product of Ciba Geigy Limited) as aphoto-polymerization initiator. ##STR16##

The resulting mixture was inserted into the panel and sealed. The UVradiation (300 nm to 400 nm, 3.5 mW/cm²) was irradiated to this panelfrom the substrate 1 side at 50° C., to polymerize the polymer precursorin the liquid crystal forming a display apparatus comprising thisembodiment. This display apparatus was subjected to a non-glaretreatment and an anti-reflection treatment on its surface. Thesetreatments, however, are not always necessary.

This display apparatus was determined for its reflectance in the absenceof an applied electric field in the same manner as Example 13. As theresult, the reflectance was 8% at 20° C. When a driver for liquidcrystal driving and a controller circuit were connected to the displayapparatus, the computer screen could be displayed with good contrast. Ofcourse, the display apparatus can also be used for terminals fortelevisions or game machines. If a color filter is incorporated todisplay element, a bright color display can be given.

As the chiral component to be used in this embodiment, singular ormultiple system as shown in Examples 12 and 15.

As the liquid crystal, polymer precursor, dichroic dye, active elementand other materials and fabrication conditions to be employed in thisembodiment, those described in Examples 1 and 12 can be employed.

As for the content of the dichroic dye, in the case where the displayelement is used for mainly giving a the transmission in the absence ofan applied electric field, for example, in the case where a solarbattery is used as a reflective plate or other display apparatus isfurther placed, the content of the dichroic dye is cut down to improvethe electric power production efficiency of the solar battery or toimprove the visibility of the display apparatus. For other uses, asdescribed in this embodiment, light absorption in the absence of anapplied electric field is fully done so that the effective contrast canbe provided.

The thickness of the liquid crystal/polymer layer is preferably 3 μm to10 μm. Too thin layer leads a low scattering property, whereas too thicklayer not only makes the required driving voltage higher but also leadsa decrease in contrast; which are practically disadvantageous.

Comparative Example 11

This embodiment is a display element fabricated according to the processof Example 16, except using only a low molecular weight chiral componentas the chiral component. That is, with the chiral liquid crystalindicated in Example 16, only a polymer precursor and aphoto-polymerization initiator were mixed and no chiral polymerprecursor was mixed. Other materials and fabrication conditions employedwere same as those of Example 16.

The display element thus fabricated was determined for its reflectancein the absence of an applied electric field. As the result, thereflectance was 10% at 20° C.

EXAMPLE 17

This embodiment is a display element in which a liquid crystalcontaining no dichroic dye is dispersed in a polymer matrix, wherein achiral polymer precursor is incorporated. At first, a panel into which aliquid crystal/polymer mixture was to be inserted was fabricated in thesame manner as Example 5. The liquid crystal/polymer precursor mixtureto be inserted into the panel is prepared in the following manner. BL007(a product of Merck Limited) as a liquid crystal was mixed with 3 wt %of R811 (a product of Merck Limited) as a chiral component with eachother, to give a chiral liquid crystal. With this chiral liquid crystal,were mixed 30 wt % of M7100 (a product of Toagosei Chemical IndustryCo., Ltd.) as a polymer precursor and 1 wt % of the following compoundas a chiral component and DETX (a product of Nippon Kayaku Company,Ltd.) as a photo-polymerization initiator. ##STR17##

The resulting mixture was inserted into the panel and sealed. The UVradiation was irradiated to this panel at 50° C.: thus a displayapparatus of this embodiment was accomplished. This display apparatusmay be subjected to a non-glare treatment or an anti-reflectiontreatment on its surface.

This display apparatus was determined for its reflectance in the absenceof an applied electric field in the same manner as Example 1. As theresult, the reflectance was 6% at 20° C.

As the chiral component to be used in this embodiment, those indicatedin Examples 12 and 15 can be employed.

As the liquid crystal, polymer precursor, a panel and other materialsand fabrication conditions to be employed in this embodiment, thosedescribed in Example 12 can be employed.

Comparative Example 12

This embodiment is a display element fabricated according to the processof Example 17, except using only a low molecular weight chiral componentas the chiral component. That is, with the chiral liquid crystalindicated in Example 17, only a polymer precursor and aphoto-polymerization initiator were mixed and no chiral polymerprecursor was mixed. Other materials and fabrication conditions employedwere same as those of Example 17. The display element thus fabricatedwas determined for its reflectance in the absence of an applied electricfield. As the result, the reflectance was 10% at 20° C.

EXAMPLE 18

This embodiment is a display apparatus combining a display element inwhich a polymer is dispersed in a liquid crystal containing dichroic dyeas particles or particles-connecting aggregates with active element,wherein a chiral component having a small temperature dependency inchiral pitch is incorporated. The same panel as Example 12 was used. Theliquid crystal/polymer precursor mixture to be inserted into the panelis explained as follows. A mixture of TL205 and MJ91261 (products ofMerck Limited) in a mixing ratio of 8:2 was used as a liquid crystal. Achiral liquid crystal was prepared by mixing 98 wt % of this liquidcrystal mixture with 2 wt % of the following compound as a chiralcomponent with each other. ##STR18##

With 96.3 wt % of the resulting chiral liquid crystal, were mixed M361,M370 and M483 (products of Mitsui Toatsu Senryo) as dichroic dyes inamounts of 1.2 wt %, 2 wt % and 0.5 wt %, respectively, to give aguest-host type chiral liquid crystal. To this guest-host type chiralliquid crystal, was dissolved 7 wt % of biphenyl methacrylate as apolymer precursor. The resultant was inserted into the panel and sealed.The UV radiation (300 nm to 400 nm, 3.5 mW/cm²) was irradiated to thispanel from the substrate 1 side at 50° C., to polymerize the polymerprecursor in the liquid crystal: thus a display apparatus of thisembodiment was accomplished. This display apparatus was subjected to anon-glare treatment and an anti-reflection treatment on its surface.These treatments is not always necessary.

This display apparatus was determined for its reflectance in the absenceof an applied electric field in the same manner as Example 13. As theresult, the reflectance was 2% at 50° C. and 3% at 20° C. When a driverfor liquid crystal driving and a controller circuit were connected tothe display apparatus, the computer screen could be displayed brightlywith good contrast. Of course, the display apparatus can also be usedfor terminals for televisions or game machines. If a color filter isincorporated to display element, a bright color display can be given.

As the chiral component to be used in this embodiment, any one may beused so long as it has a small temperature dependency in chiral pitch.In particular, the chiral component exhibiting a changing rate in chiralpitch of 20% or less within use temperature range where the displayelement is used is more preferable. If the changing rate in chiral pitchis over 20%, the display contrast becomes remarkably decreased due tothe temperature change during the display element is used. Examples ofthe chiral component to be used in this embodiment include the followingcompounds: ##STR19##

Besides them, CNL611, CNL621, CNL617, CNL616 and CNL623 (products ofAsahi Denka Kogyo, K.K.) can also be used. The multiple system of chiralcomponents, as indicated in Example 15, may also be used.

As the liquid crystal and polymer precursor, those indicated in Example1 can be used.

The thickness of the liquid crystal/polymer layer is preferably 3 μm to10 μm. Too thin layer leads a low scattering property, whereas too thicklayer not only makes the required driving voltage higher but also leadsa decrease in contrast; which are practically disadvantageous.

The active element to be used in this embodiment is not limited to theMIM element indicated in this embodiment, and those which have atransistor structure, such as polysilicon TFT elements and amorphoussilicon TFT elements, those which have a MIM structure, ferroelectricelements may be used. The number of the active elements to be used isnot also limited to the number indicated in this embodiment, and it maydetermined according to the intended use. Of course, if without activeelement, the display element of this embodiment can be operated by asimple matrix type drive or a static drive.

In this embodiment, reflective electrode 7 may be a transparentelectrode (with high refractive index), and a reflective layer or asolar battery may be placed on the back surface of the display element.The reflective layer may, in addition, be imparted with a lightscattering property.

Comparative Example 13

This embodiment is a display apparatus fabricated according to theprocess of Example 18, except using only a chiral compound having apositive temperature dependency in chiral pitch as the chiral component.That is, 2.5 wt % of CB15 (a product of Merck Limited) as a chiralcomponent was mixed with the liquid crystal. Other materials andfabrication conditions employed were same as those of Example 18. Thedisplay element thus fabricated was determined for its reflectance inthe absence of an applied electric field. As the result, the reflectancewas 2% at 50° C. and 5% at 20° C.

EXAMPLE 19

This embodiment is a display element which contains no dichroic dye andwherein a liquid crystal and a polymer are dispersed to each other,wherein chiral component having a small temperature dependency in chiralpitch is used. A panel with no active element was fabricated in the samemanner as Example 5. The liquid crystal/polymer precursor mixture to beinserted into the panel is explained as follows. A mixture of RDP80616-2(a produce of Rodic Inc.) and ML1009 (a product of Merck Limited) in amixing ratio of 7:3 was used as a liquid crystal. A chiral liquidcrystal was prepared by mixing this liquid crystal mixture with 2 wt %of CNL617 (a product of Asahi Denka Kogyo, K.K.) as a chiral componentwith each other. The resulting chiral liquid crystal was mixed with 4 wt% of methyl terphenyl methacrylate as a polymer precursor. The resultantwas inserted into the panel and sealed. The UV radiation was irradiatedto this panel at 50° C. Thus, a display apparatus of this embodiment wasaccomplished. This display apparatus may be subjected to a non-glaretreatment or an anti-reflection treatment on its surface.

This display apparatus was placed with a solar battery on its backsurface to give a reflection-type of display element. The resultant wasdetermined for its reflectance in absence of an applied electric fieldin the same manner as Example 18. As the result, the reflectance was 1%at 50° C. and 3% at 20° C. When an electric field was applied, thedisplay element could be used for a segment display for a watch.

In this embodiment, no active element was used. However, if used, sameeffect might be given. In such case, the liquid crystal having a goodretention characteristic should be used, as shown in Example 1. It ispreferable to use, for example, TL202, TL204, TL205, TL213, TL215, TL216as a base. If incorporating with a color filter, a bright color displaycan be provided. In the case where no active element is used, anymaterial may be employed as a liquid crystal so long as it shows anematic type liquid crystal phase.

The thickness of the liquid crystal/polymer layer is preferably 3 μm to10 μm. Too thin layer leads a low scattering property, whereas too thicklayer not only makes the required driving voltage higher but also makedecrease in contrast; which are practically disadvantageous.

In stead of the solar battery, a light absorbing layer and a lightreflecting layer may be placed on the back surface of the displayelement. If without placing anything on the back surface, this displayelement can also display as white scattering on a transparent glass.

In this embodiment, other materials and fabrication conditions were sameas those of Example 18. The chiral components shown in Example 15 mayalso be used in this embodiment.

Comparative Example 14

This embodiment is a display apparatus fabricated according to theprocess of Example 19, except using only a chiral compound having apositive temperature dependency in chiral pitch as the chiral component.That is, 5 wt % of CB15 (a product of Merck Limited) was mixed with theliquid crystal. Other materials and fabrication conditions employed weresame as those of Example 19.

The display element thus fabricated was determined for its reflectancein the absence of an applied electric field. As the result, thereflectance was 1% at 50° C. and 3% at 20° C.

EXAMPLE 20

This embodiment is a display apparatus combining a display element inwhich a liquid crystal containing dichroic dye is dispersed in a polymergel network with active element, wherein a chiral component having asmall temperature dependency in chiral pitch is incorporated. A panelwith formation of TFT element was fabricated in the same manner asExample 2. The liquid crystal/polymer precursor mixture to be insertedinto the panel is explained as follows. A mixture of TL205 and BL007(products of Merck Limited) in a mixing ratio of 7:3 was used as aliquid crystal. A chiral liquid crystal was prepared by mixing 98 wt %of this liquid crystal mixture with 2 wt % of CNL611 (a product of AsahiDenka Kogyo, K.K.) as a chiral component with each other. With 96.3 wt %of the resulting chiral liquid crystal, were mixed M361, M370 and M483(products of Mitsui Toatsu Senryo) as dichroic dyes in amounts of 1.2 wt%, 2 wt % and 0.5 wt %, respectively, to give a guest-host type chiralliquid crystal. With 97 wt % of this guest-host type chiral liquidcrystal, was mixed 3 wt % of a polymer precursor employed in Example 8.The resultant was inserted into the panel and sealed. The TV radiation(300 nm to 400 nm, 3.5 mW/cm²) was irradiated to this panel from thesubstrate 1 side at 50° C., to polymerize the polymer precursor in theliquid crystal: thus a display of this embodiment was accomplished. Thisdisplay apparatus was subjected to a non-glare treatment and ananti-reflection treatment on its surface. These treatments are notalways necessary.

This display apparatus was determined for its reflectance in the absenceof an applied electric field. As the result, the reflectance was 2% at50° C. and 3% at 20° C. When a driver for liquid crystal driving and acontroller circuit were connected to the display apparatus, the computerscreen could be displayed brightly with good contrast. Of course, thedisplay apparatus can also be used for terminals for televisions or gamemachines. If a color filter is incorporated to display element, a brightcolor display can be given.

As the chiral component, liquid crystal, polymer precursor, activeelement and the fabrication conditions, those indicated in Example 2 canbe employed. In particular, as for the chiral component, the multiplesystem indicated in Example 15 may also be used.

The thickness of the liquid crystal/polymer layer is preferably 3 μm to10 μm. Too thin layer leads a low scattering property, whereas too thicklayer not only makes the required driving voltage higher but also leadsa decrease in contrast; which are practically disadvantageous.

Comparative Example 15

This embodiment is a display apparatus fabricated according to theprocess of Example 20, except using only a chiral compound having apositive temperature dependency in chiral pitch as the chiral component.In particular, 2 wt % of CB15 (a product of Merck Limited) as a chiralcomponent was mixed with the liquid crystal. Other materials andfabrication conditions employed were same as those of Example 20.

The display element thus fabricated was determined for its reflectancein the absence of an applied electric field. As the result, thereflectance was 3% at 50° C. and 10% at 20° C.

EXAMPLE 21

This embodiment is a display element in which a liquid crystalcontaining no dichroic dye is dispersed in a polymer gel network,wherein a chiral component having a small temperature dependency inchiral pitch is incorporated. A panel into which a liquidcrystal/polymer precursor mixture was to be inserted was fabricated inthe same manner as Example 5. The liquid crystal/polymer precursormixture to be inserted into the panel is explained as follows. BL007 (aproduct of Merck Limited) as a liquid crystal was mixed with 10 wt % ofCM22 (a product of Chisso Corporation) and 2.5 wt % of CB15 (a productof Merck Limited) as chiral components, to give a chiral liquid crystal.The resulting chiral liquid crystal was mixed with 3 wt % of C₆ H usedin Example 8 as a polymer precursor. The resultant was inserted into thepanel and sealed. The UV radiation was irradiated to this panel at 50°C. The display element thus fabricated may be subjected to a non-glaretreatment or an anti-reflection treatment on its surface.

On the back surface of this display element, a solar battery was placed,to give a reflection type of display element. The resulting displayelement was determined for its reflectance in the absence of an appliedelectric field in the same manner as Example 1. As the result, thereflectance was 2% at 50° C. and 5% at 20° C.

As the chiral component to be used in this embodiment, those which wereindicated in Example 15 can be employed.

As the liquid crystal, polymer precursor, a panel and other fabricationconditions, those indicated in Example 19 can be employed.

Comparative Example 16

This embodiment is a display apparatus fabricated according to theprocess of Example 21, except using only a chiral compound having apositive temperature dependency in chiral pitch as the chiral component.That is, 5 wt % of CB15 (a product of Merck Limited) as a chiralcomponent was mixed with the liquid crystal. Other materials andfabrication conditions employed were same as those of Example 21.

The display element thus fabricated was determined for its reflectancein the absence of an applied electric field. As the result, thereflectance was 1% at 50° C. and 3% at 20° C.

EXAMPLE 22

This embodiment is color display apparatus with a color filter, whereinthe embodiments described above are applied. FIG. 7 is a simple, partialsectional view of a panel used in this embodiment, in which a colorfilter is formed. The materials other than a color filter andfabrication conditions were same as those of each embodiment. In thisembodiment, dichroic dye was not added. However, for the purpose ofimproving display contrast, dichroic dye may be added to the colordisplay apparatus. When a liquid crystal driver for color display wasconnected to this color display apparatus to be used as a computerterminal, color display was provided with good contrast. Of course, thedisplay apparatus can also be used the display of watches, televisionsor game machines.

As the construction or composition and the fabrication conditions of thechiral component, liquid crystal/polymer layer, panel to be used in thisembodiment, those indicated in Examples 1 to 21. The color displayelement of this embodiment can also be applied to the electronicapparatus as describe below.

As for the color filter to be used, one having a lighter tone than theconventional transmission-type color filters can give a brighterdisplay. The colors to be displayed in this color display apparatus canbe freely select from the colors which can be displayed in a colordisplay, such as three primary colors (i.e. red, blue and green) andyellow, cyan, magenta.

As for the position where a color filter is to be formed, in thisembodiment, a color filter was formed on the liquid crystal-contactingside of the substrate 1 positioning in the display side of the displayapparatus. However, the color filter may also be formed on the substrate8. From viewpoint of the required driving voltage, it is preferable toform the color filter between a substrate and an electrode. Atransparent electrode may be formed on the color filter.

In the case where the color filter is formed on the substrate 1, thecolor filter should be made of a material which can transmit UVradiation used for the polymer precursor polymerization.

The active element is not limited to the TFT element indicated in thisembodiment, and other TFT elements having other structures, transistors,MIM elements, ferroelectric elements and the like may be used. As thesubstrate to be formed with such active element thereon, can beemployed, for example, semi-conductors such as glass, silicon, arsenicgallium and germanium, other inorganic substances and organic substancessuch as plastics. In the display element according to the presentinvention, all of a driving driver and a controller can be built or setinto the substrates. Therefore, by using the display element, a displayapparatus can be fabricated in extremely low cost.

EXAMPLE 23

This embodiment is electronic memorandum book, which is one kind ofinformation processing apparatus, incorporated with the display elementsany of the above described Examples and Comparative Examples as thedisplay. FIG. 8 is a schematic sectional view of the informationprocessing apparatus according to this embodiment. A display element wasfabricated according any of foregoing Examples or Comparative Examples,and then placed with a solar battery on their back surface. When theelectric power of the solar battery was connected to the power source ofthe electronic memorandum book, its visibility became improved, andfurthermore the amount of time the electronic memorandum book could beused became remarkably increased.

In the electronic apparatus of this embodiment, the solar battery may beconnected to a storage battery built in the apparatus to store theelectric power produced by the solar battery in the storage battery, bywhich the electronic apparatus can be operated effectively even in thedark circumstances.

In the conventional electronic memorandum book, since a solar batteryoccupies a large space, the design and size have been limited. In theelectronic memorandum book according to this embodiment, on thecontrary, since a display element used is almost transparent, a displaypanel can be superposed on a solar battery, resulting in realization ofan extremely compact electronic memorandum book with no trouble inrunning down of battery.

This display apparatus may be placed with an information input devicesuch as a tablet or a touch-type panel placed on its back surface.

EXAMPLE 24

This embodiment is illustrated in FIG. 9 showing a watch in schematicform, which is one form of an information display apparatus with whichthe display element of this invention may be utilized as set forth inany of the previously described Examples and Comparative Examples.Display element 21 is provided with an aperture at its center sealedfrom the PDLC medium contained with the element. Solar battery 22 wasplaced on the back surface of display element 21, and the drive shaftfor the hands of analog type watch 26 were inserted through the centralaperture of display element 21 forming a hybrid type watch. Displayelement 21 had good display properties with a high degree of visibilityresulting for both watch 26 and the digital display at 21.

In the display apparatus of this embodiment, the solar battery may beconnected to a storage battery built in the apparatus to store theelectric power produced by the solar battery in the storage battery, bywhich the apparatus can be operated effectively even in the darkcircumstances.

This display apparatus could not be driven effectively with the voltagesupplied from the solar battery. However, when a booster circuit wasincorporated into the apparatus and the voltage of the solar battery wasboosted to 5 V, the display apparatus showed an extremely brightdisplay.

As one of the driving methods for this display apparatus, the ground ofthe liquid crystal driver may be shaken in times to the driving timing.This method can make the voltage applied to the display apparatussubstantially double the source voltage. As the result, by this method,the display elements described in the above embodiments can be driveneffectively and an extremely bright display can be provided.

The display elements of Examples described above are fairly low electricpower consumption type. In order to further elongate the battery life ofthe watch, the watch may be designed so that the display of the displayelement is provided only in the switch-ON state.

In this embodiment, in stead of the solar battery, a light-absorbingplate may be used, by which the same level of display can be provided.In this case, the driving power source is only a built-in battery.

EXAMPLE 25

This embodiment is watch, which is one kind of information displayapparatus, incorporated with the display elements of above describedExamples and Comparative Examples. In particular, in this embodiment,shown in FIG. 10, display element 21 is employed as a cover glass for ananalog mode watch 26 with solar battery 22 employed at the back surfacefor the clockface of watch 26 forming a self-power hybrid type of watch.Watch 26 had good display properties with a high degree of visibilityresulting for both display element 21 and the watch display at 26.

In this embodiment, a construction other than the one described abovewas same as in the case of Example 24.

EXAMPLE 26

This embodiment is a portable television as an information displayapparatus, to which one of the display elements of above-describedExamples and Comparative Examples are applied as shown in FIG. 11. Adisplay element was fabricated according to one of above describedExamples or Comparative Examples, and then a solar battery 22 was placedon its back surface. When the resultant was incorporated into a portabletelevision body, a good display with an extremely high visibility couldbe provided, and furthermore the amount of time the television could beused became remarkably increased.

In this embodiment, the constructions other than described above wassame as those of Example 24.

In the conventional portable information display apparatus (i.e.television), since a solar battery occupies a large space, the designand size have been limited. In the information display apparatusaccording to this embodiment, on the contrary, since a display elementused is almost transparent, a display panel can be superposed on a solarbattery, resulting in realization of an extremely compact electronicinformation display apparatus with no trouble in running down ofbattery.

EXAMPLE 27

This embodiment is a display apparatus in which the display elements ofabove-described Examples and Comparative Examples are superposed with adisplay element 21 overlying a highly refractive layer 29 overlying ananalog mode watch surface 26 having hour/minutes hands, as schematicallyillustrated in FIG. 12. This display element could be fully driven witha conventional IC designed for watch. This display element 21 wassuperposed on a dark clockface at surface 26. In this time, on thesurface of the flat dark clockface, ITO (refractive index: 1.8) wasvapor-evaporated as a highly refractive layer. When date, time and Clockresistor function were made to display on the two-layer type of displayapparatus thus fabricated, a digital display could be provided withlarge letters on the clockface of the conventional analog-type watch;which was highly functional and fashionable. The brightness of thisdisplay apparatus became brighter by 1.5 times that of the apparatuswithout highly refractive layer.

In this embodiment, the constructions other than described above wassame as those of Example 24.

The display apparatus of this embodiment can be used as a displayportion of a meter for a machine, a domestic electric product and anelectronic apparatus, as well as a wrist watch and a table clock. Thisdisplay apparatus may be any type, such as an analog mode, a digitalmode or a hybrid mode. However, the clockface is preferably dark tone orreflective type, so that the resultant display becomes clearer incontrast and visibility. When a background comprising a solar battery 22is used as the clockface and the electric power produced by the solarbattery is used as the driving power source of the watch or clock, thelife of the battery can be remarkably increased.

As the material of the highly refractive layer to be employed, besidesITO, any one may be used so long as it has a high refractive index.Examples of such material include glass materials having a highrefractive index, e.g. FDS1, a product of HOYA Corporation with arefractive index of 2, inorganic oxides, thin metal films, films oforganic substances and polymers (preferably polymer films containingmultiple aromatic rings, such as terphenyl, perylene and tetracene. Asto the particular position or location of the highly refractive layer,those positions illustrated in FIGS. 13 and 14 are equally effective.

This embodiment may also be applied to vehicle meter display panels,other mechanized meters, displays of domestic electric products andelectronic apparatus. The use of this display apparatus enables thedisplay of both an analog display and a digital display in a smalldisplay window. Particularly, the massiveness of analog display is notimpaired, and therefore this display apparatus is suitable for the usewhere high display quality is required. Of course, if applied to adigital display apparatus (such as twisted nematic type liquid crystalelement, LED, VFD, plasma display), the display apparatus of thisinvention can provide the same effect as in the case of more compact orminiaturized applications.

EXAMPLE 28

This embodiment is a vehicle meter display panel employing a displayapparatus having the display element of Example 23. As shown in FIG. 15,the liquid crystal layer 31 containing dichroic dye is positionedbetween display apparatus 30 of the back side and display element 21 offront side. Layer 31 containing dichroic dye is provided between a pairof transparent substrates with electrodes formed on their respectivesurfaces, which have been subjected to an alignment treatment. Thespaced support of the substrates is formed to provided a 7 μm betweenthe substrates. The liquid crystal/polymer layer comprises a liquidcrystal mixture of ZLI1840 (a product of Merck Limited), S344 (a productof Mitsui Toatsu Senryo) and CB15 (a product of Merck Limited) in amixing ratio of 95:3:2. The liquid crystal materials and their mixingratio are optimized according to the intended use.

If the display of display element 21 of the front side is intended totransparent. The electric field is controlled to render the liquidcrystal layer containing dichroic dye to have a light absorbing state sothat the displayed information is of high contrast through the lightscattering mode. In this case, instead of the reverse PDLC, aconventional PDLC may be used. On the other hand, if display 30 of thedisplay apparatus at the back surface has an applied electric field thatis controlled opposite to that of the applied electric field for layer31 containing dichroic dye, the back surface display will be transparentthrough the liquid crystal/polymer layer 31.

The liquid crystal layer 31 containing dichroic dye is not limited tothe liquid crystal having a positive dielectric anisotropy indicated inthis embodiment, as liquid crystal materials having a negativedielectric anisotropy may also be employed. In such a case, it ispreferred to apply a homeotropic treatment to the surfaces of thesubstrates sandwiching the liquid crystal medium, by which, contrary tothe case described above, the liquid crystal layer becomes transparentin the absence of an applied electric field and absorbs light in thepresence of an applied field.

In FIG. 15, a highly refractive layer 29 can be placed in front ofliquid crystal/polymer layer 31. However, as illustrated in FIG. 16, thedisplay is still effective without the use of refractive layer 29.

This embodiment can also be applied to the vehicle meter display panels,other mechanized meters, displays of domestic electric products andelectronic apparatus. The use of this display apparatus enables theconcurrent, superimposed use of both types of displays of the analog anddigital mode in a single display window. In particular, the larger sizeof analog display is not impaired and, therefore, this display apparatusis readily suitable for the use where high display quality ofsuperimposed images is required. If a panel according to Example 2 orComparative Example 2 employing a transparent layer 28, instead ofrefractive layer 29, as shown in FIG. 17, and is superposed on analogmeter 30, the resulting display apparatus may be employed as a displayfor the vehicle navigation system, television receiver or videoprojector. In this case, a vehicle motorist can easily see the displayduring driving while still facing the forward in the direction of travelthereby maintaining a safe driving condition.

The display apparatus of this embodiment will provide an equal effect asapplied to a digital mode display apparatus, e.g., a twisted nematictype liquid crystal element, LED, VFD, plasma display, or the like.

In summary, this invention comprises the application of PDLC medium or areverse PDLC medium having a predetermined amount of dichroic dye addedto the liquid crystal of the medium with the medium being selected tohave a low fluorescence quantum yield wherein a reduced temperaturedependency effect relative to a difference in the chiral twist of theliquid crystal layer before polymerization and after polymerization witha significant reduction in haze and a corresponding significant increasein the visibility of the display element incorporating such a medium.The haze reduction technique of this invention is very effective foraesthetic and fashion-conscience applications such as in the case of awatch. For example, in a wrist watch, when a reverse PDLC displayelement is positioned as a clockface of the watch or as a cover glassfor the watch, the haze created by the PDLC display element is almostinconspicuous resulting in high contrast. Thus this display element hasapplication with any type of electronic apparatus either by superposingthe reverse PDLC display element directly on a conventional displayapparatus or directly on a solar battery or with an interposing highlyrefractive layer, a bright, multi-functional electronic apparatus with ahigh visibility can be realized.

The use of a display element or an electronic apparatus employing thedisplay element of this invention enables manufacturer of wrist watches,table clocks, domestic electric products and electronic apparatus with avery large capacity with high image visibility. Furthermore, in the casewhere a solar battery is built into or integrated with the displayelement or apparatus, the resulting display element and apparatus arecompact having high image visibility and low electric power consumption.For example, due to the employment of the PDLC environment taught bythis invention technique, the reverse PDLC medium itself effectivelyfunctions as the cover glass of the electronic device or the clockfaceof an analog mode watch overlying a solar battery. Accordingly, a watchimparted with both the beauty of an analog mode watch and themulti-functionality of a digital mode watch can be provided in asuperimposed fashion with clear imagery of the displayed information.

On the other hand, when the PDLC environment taught by this inventiontechnique is employed as the display portion of an electronic memorandumbook or a potable television, even in the case where a solar battery isbuilt into the structure, an extremely compact electronic memorandumbook or a potable television with high visibility can be provided.Particularly those incorporated with a solar battery can be employedwithout the problem of running down the battery.

The display element and apparatus of the present invention can also beemployed as an meter vehicle panel with good visibility. For example, areverse PDLC panel is placed on the surface of a conventional analogmode display apparatus employed as a panel in vehicles. Then, the backsurface analog display is illuminated by means of a back light and thefront display panel is illuminated from the front side so that the frontdisplay will stand out visually on the analog display at the backsurface creating a combination display having excellent visibility.Since the display element of this invention can be placed on aconventional mechanized meter type display, the range of application ofthe invention is of wide utility. The display element for electronicapparatus of this invention is basically of the reflective type, and itsdisplayed image visibility improves with ambient brightness. Therefore,the deterioration of visibility brought about with electronic apparatusof the self-emission type and back light type is eliminated. Inaddition, in the case where a display element employing a conventionalback light type or reflective type of twisted nematic liquid crystalmedium is positioned on the back surface of a display element utilizingthe PDLC medium of this invention, improved visibility of both displayelements is achieved relative to their superimposed, generated images.

While the invention has been described in conjunction with severalspecific embodiments, it is evident to those skilled in the art thatmany further alternatives, modifications and variations will be apparentin light of the foregoing description. Thus, the invention describedherein is intended to embrace all such alternatives, modifications,applications and variations as may fall within the spirit and scope ofthe appended claims.

What is claimed is:
 1. An electronic apparatus comprising:a displayapparatus displaying a first information and a separate display elementdisplaying a second information, said display element comprising aliquid crystal and polymer medium formed between a pair of spatiallysupported substrates, said substrates each having an electrode on onesurface thereof, and means for applying an electric field across saidmedium via said electrodes wherein said medium is placed in a lighttransmissive state in the absence of the applied electric field and isplaced in a light scattering state in the presence of the appliedelectric field, said electronic apparatus displaying a superimposedinformation of both the second information of said display element bylight scattering and the first information of said display apparatus,wherein said liquid crystal portion includes a chiral component andthereby exhibits a variation of chiral pitch not exceeding 20% of anoperating range of temperature for the display element.
 2. Theelectronic apparatus according to claim 1 wherein a pitch of said chiralcomponent in said medium is substantially the same as the pitch inliquid crystal portion of said liquid crystal and polymer medium.
 3. Theelectronic apparatus according to claim 1 wherein said chiral componentcomprises a low molecular weight chiral component and a chiral polymerprecursor, said chiral polymer precursor is incorporated into thepolymer portion of said liquid crystal-polymer medium and said lowmolecular weight chiral component is incorporated into the liquidcrystal portion of said liquid crystal-polymer medium.
 4. The electronicapparatus according to claim 1 wherein said chiral component comprisesat least two chiral components exhibiting an opposite temperaturedependency in chiral pitch relative to each other.
 5. The electronicapparatus according to claim 1 wherein said liquid crystal and polymermedium includes a compound exhibiting a fluorescence quantum yield inthe visible region of not more than 0.3 and is provided in said mediumin an amount of not less than 60 wt %.
 6. The electronic apparatusaccording to claim 5 wherein said liquid crystal portion includes saidcompound comprising a biphenyl or tolane skeleton in its molecularcomposition.
 7. The electronic apparatus according to claim 6 whereinsaid compound has a terphenyl skeleton in its molecular composition inthe liquid crystal portion in an amount not exceeding about 10%.
 8. Theelectronic apparatus according to claim 5 wherein said polymer portionincludes said compound comprising a biphenyl or tolane skeleton in itsmolecular composition.
 9. The electronic apparatus according to claim 8wherein said compound has a terphenyl skeleton in its molecularcomposition in the polymer portion in an amount not exceeding about 10%.10. The electronic apparatus according to claim 1 wherein the liquidcrystal portion includes a dichroic dye.
 11. The electronic apparatusaccording to claim 1 wherein said polymer is in a form selected from thegroup consisting of independent particles, chain connected particles,coupled particles, and particle aggregates.
 12. The electronic apparatusaccording to claim 1 wherein said polymer is a gel network.
 13. Theelectronic apparatus according to claim 1 wherein said polymer dispersedin the liquid crystal portion in the form of droplets.
 14. Theelectronic apparatus according to claim 1 wherein a non-glare,anti-reflecting surface is provided on one surface of said displayelement.
 15. The electronic apparatus according to claim 1 wherein acolor filter is employed on a surface of one of said substrates incontact with liquid crystal and polymer medium.
 16. The electronicapparatus according to claim 1 wherein said display element furthercomprises a plurality of active elements formed on a surface of one ofsaid substrates in contact with said liquid crystal and polymer medium.17. The electronic apparatus according to claim 1 wherein said polymerportion contains at least one of the following compounds: ##STR20##wherein n is an integer; R represents an alkyl, alkoxy, cycloalkyl, orcycloalkoxy group; R₁ and R₂ independently represent an alkyl,cycloalkyl, alkoxy or cycloalkoxy group or H or F; and X represents H,F, Cl or CN.
 18. The electronic apparatus according to claim 1 whereinsaid polymer portion contains at least one of the following compounds:##STR21## wherein R and R' are respectively either H or CH₃ ; B, B' andB" are respectively any one of OCO, COO, OCONH, NHCOO, CONH, NHCO,--C.tbd.C--, an alkyl group, O, N or S; and A₁ and A₂ are respectively agroup containing an aromatic ring comprising phenyl, biphenyl,terphenyl, quaterphenyl, naphthalene and anthracene with substitutionthereof selected from the group consisting of a halogen, alkyl group andcyano group.
 19. The electronic apparatus according to claim 1 whereinone of said substrates includes a reflective surface.
 20. The electronicapparatus according to claim 1 further comprising a light absorbingreflective plate positioned on a back surface of said display element.21. The electronic apparatus according to claim 20 wherein said lightabsorbing reflective plate comprises a solar battery.
 22. An electronicapparatus comprising:a display apparatus displaying a first informationand a separate display element displaying a second information, saiddisplay element comprising a liquid crystal and polymer medium formedbetween a pair of spatially supported substrates, said substrates eachhaving an electrode on one surface thereof, and means for applying anelectric field across said medium via said electrodes wherein saidmedium is placed in a light transmissive state in the absence of theapplied electric field and is placed in a light scattering state in thepresence of the applied electric field, said electronic apparatusdisplaying a superimposed information of both the second information ofsaid display element by light scattering and the first information ofsaid display apparatus, said electronic apparatus further comprising arefractive layer positioned between said display element and saiddisplay apparatus, wherein said liquid crystal portion includes a chiralcomponent and thereby exhibits a variation of chiral pitch not exceeding20% of an operating range of temperature for the display element. 23.The electronic apparatus according to claim 22 wherein said refractivelayer is transparent.
 24. The electronic apparatus according to claim 1wherein said liquid crystal and polymer medium includes a dichroic dye.25. The electronic apparatus of claim 16, wherein said active elementsare selected from the group consisting of TFT, MIM, transistor andferroelectric elements.
 26. The electronic apparatus according to claim1, wherein said display element is selected from the group consisting ofa watch, an automobile meter display panel, an electronic memorandumbook, and a display of a domestic electric product.